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1

Functional Monomers and Polymers. 90 Radiation-Induced Graft Polymerization of Styrene onto Chitin and Chitosan  

Microsoft Academic Search

The graft polymerization of styrene onto chitin powder, and chitosan powder and film initiated by ?-ray irradiation was carried out at 30°C. The graft polymerization was found to proceed predominantly in the presence of water, and the degree of grafting increased with an increase in the radiation dose. From ESR spectroscopy it was noted that the free radicals generated both

Yasuhiro Shigeno; Koichi Kondo; Kiichi Takemoto

1982-01-01

2

Radiation induced graft polymerization of a fluorinated acrylate onto fabric  

NASA Astrophysics Data System (ADS)

A fluoride acrylate monomer, 1H,1H,2H,2H-nonafluorohexyl-1-acrylate (denoted as F4), was grafted onto cotton fabric through a simultaneous irradiation induced graft polymerization technique. The grafted cotton fabric (denoted as cotton-F4) is superhydrophobic (SCF) when the degree of grafting (DG) exceeded 10%. The morphology of the cotton fabric was unchanged. In addition, the mechanical properties of the cotton fabric and SCF samples were also studied. The results showed that the decrease in mechanical properties was less than 20%, indicating that the SCF retained good mechanical strength.

Cai, Ren; Deng, Bo; Jiang, Haiqing; Yu, Yang; Yu, Ming; Li, Linfan; Li, Jingye

2012-09-01

3

Radiation-induced graft polymerization of amphiphilic monomers with different polymerization characteristics onto hydrophobic polysilane  

NASA Astrophysics Data System (ADS)

The structures of poly(methyl-n-propylsilane) (PMPrS) amphiphilically modified through ?-ray-induced graft polymerization were investigated with 1H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreased with increasing dose rate. This result means that grafting yield of modified PMPrS can be controlled by changing irradiation conditions. However, the number of PMMA or PDEF graft chains per PMPrS chain was estimated to be less than 1.0 by analysis of 1H NMR spectra, and this value was lower than that we had expected. To improve graft density, maleic anhydride (MAH), which is known as a non-homopolymerizable monomer in radical polymerization, was used as a monomer for grafting. As a result, high density grafting (one MAH unit for 4.2 silicon atoms) was attained. It demonstrates that the structure of ?-ray-modified polysilane strongly depends on the polymerization characteristics of grafted monomers.

Tanaka, Hidenori; Iwasaki, Isao; Kunai, Yuichiro; Sato, Nobuhiro; Matsuyama, Tomochika

2011-08-01

4

Antimicrobial fabric adsorbed iodine produced by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Antimicrobial fabric was synthesized by radiation-induced graft polymerization of N-vinyl pyrrolidone onto polyolefine nonwoven fabric and subsequent adsorption of iodine. In response of the huge request for the antimicrobial material applied to face masks for swine flu in 2009, operation procedure of continuous radiation-induced graft polymerization apparatus was improved. The improved grafting production per week increased 3.8 times compared to the production by former operation procedure. Shipped antimicrobial fabric had reached 130,000 m2 from June until December, 2009.

Aoki, Shoji; Fujiwara, Kunio; Sugo, Takanobu; Suzuki, Koichi

2013-03-01

5

Graft polymerization using radiation-induced peroxides and application to textile dyeing  

NASA Astrophysics Data System (ADS)

To improve the dyeing affinity of ultra high molecular weight polyethylene (UHMWPE) fiber, surface treatment by radiation-induced graft polymerization was performed. Methyl methacrylate (MMA), acrylic acid (AA) and styrene (St) were used as the monomers. The grafting yields as a function of storage time after irradiation were examined. Although the grafting yield of St after the sulfonation processing was quite low compared with those of MMA and AA, it was successfully dyed to a dark color with a cationic dye. Some acid dyes can dye the grafted fiber with AA. The acid dye is distributed to the amorphous domains of the AA grafted fiber. The dyeing concentration depended on the grafting yield, and the higher the grafting yield the darker the dye color.

Enomoto, Ichiro; Katsumura, Yosuke; Kudo, Hisaaki; Soeda, Shin

2011-02-01

6

Radiation-induced graft polymerization of N-vinylpyrrolidone onto segmented polyurethane based on isophorone diisocyanate  

NASA Astrophysics Data System (ADS)

A segmented polyurethane (PUR) sample based on isophorone diisocyante was modified by radiation induced-graft polymerization of N-vinylpyrrolidone. Radiation grafting was carried out by the mutual irradiation method to improve hydrophilicity of the matrix surface. Different parameters affecting the grafting yield, such as effect of dose, monomer and mineral salt concentration, were investigated. It was found that degree of grafting increased with increasing total dose and monomer concentration in the presence of small amount of homopolymer suppressor. Physicochemical properties of the control and grafted PUR were studied using infrared spectroscopy (ATR-FTIR), thermogravimetric analysis, atomic force microscopy and X-ray photoelectron spectroscopy. The wettability was evaluated by contact angle measurements.

Walo, Marta; Przybytniak, Gra?yna; Kavakl?, P?nar Akkas; Güven, Olgun

2013-03-01

7

Graft copolymers of polyurethane with various vinyl monomers via radiation-induced miniemulsion polymerization: Influential factors to grafting efficiency and particle morphology  

NASA Astrophysics Data System (ADS)

Graft copolymers of polyurethane (PU) with various vinyl monomers were synthesized through a one-pot but two-step miniemulsion polymerization process. Firstly, the polycondensation of isophorone diisocyanate (IPDI) with hydroxyl-terminated polybutadiene (HTPB) had been performed in aqueous miniemulsion at 40 °C in order to obtain PU dispersions. Consecutively, an in-situ graft copolymerization of the vinyl monomers with the synthesized PU was initiated by ?-ray radiation at room temperature. The grafting efficiency of PU with vinyl monomer ( GPU/monomer) was calculated from 1H NMR spectra and the particle morphology of the final hybrid latex was observed by transmission electron microscopy (TEM). As there was no monomer transferring in miniemulsion system, homogenous hybrid particles would be synthesized provided that the monomer was miscible with PU, such as styrene. With the increase of the polarity of the monomer, the compatibility of PU with monomer decreased. GPU/monomer varied as GPU/styrene(37%)> GPU/butyl acrylate (BA)(21%)> GPU/methyl methacrylate (MMA)(12%). The proportion of homogeneous nucleation would increase as the hydrophilicity of the monomer increased. High temperature would destabilize the miniemulsion so as to result in a less grafting efficiency. Compared to the phase separation during the seeded emulsion polymerization, the miniemulsion polymerization method facilitated the preparation of homogeneous materials owing to its monomer droplet nucleation mechanism.

Wang, Hua; Wang, Mozhen; Ge, Xuewu

2009-02-01

8

Protein adsorption characteristics of porous and tentacle anion-exchange membrane prepared by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

A polymer chain containing a diethylamino group was grafted onto the pore surface of a porous hollow-fiber membrane by radiation-induced graft polymerization. Dependence of the protein binding capacity of the membrane on environmental parameters such as salt concentration, pH and temperature was investigated. Saturation capacity of protein bound onto the graft chain containing ion-exchange group was governed by the conformation of the graft chain and the intensity of ion-exchange interaction. The conformation of the graft chain was investigated based on the pore radius of the membrane estimated from the permeation flux of a buffer solution through the membrane. By sufficiently permeating a bovine serum albumin (BSA) solution within the concentration range of 0.2-10 mg-BSA/ml through the membrane, the BSA binding capacity was determined. With increasing salt concentration or pH of the protein buffer solution, the graft chain shrank and BSA binding capacity decreased. On the other hand, the BSA binding capacity slightly increased with increasing temperature, and the conformation of the graft chain was insensitive to temperature in the range from 278 to 303 K. The bound BSA could be quantitatively eluted by permeating a buffer solution containing 0.5 M NaCl, and no deterioration in the BSA binding capacity was observed during five cycles of adsorption, elution and conditioning.

Tsuneda, Satoshi; Saito, Kyoichi; Sugo, Takanobu; Makuuchi, Keizo

1995-08-01

9

The role of hydroperoxides as a precursor in the radiation-induced graft polymerization of methyl methacrylate to ultra-high molecular weight polyethylene  

NASA Astrophysics Data System (ADS)

A graft polymerization of methyl methacrylate (MMA) to ultra-high molecular weight polyethylene (UHMWPE) with Co-60 ?-ray irradiation in air at room temperature has been carried out. The grafting yields were measured as a function of the storage time (elapsed time from the end of irradiation to the start of grafting), and it was found that the yields reach at the maximum values at around several days since the end of irradiation. In order to clarify the precursor of the graft polymerization, changes of the radical yields and the carbonyl groups were measured as a function of storage time with ESR and microscopic FT-IR, respectively. From the similarities between the depth profiles of the hydroperoxide formation and the grafting products, it was concluded that the hydroperoxides can be main precursors of the grafting of the radiation-induced polymerization of MMA to UHMWPE under the given conditions.

Enomoto, Ichiro; Katsumura, Yosuke; Kudo, Hisaaki; Sekiguchi, Masayuki

2010-06-01

10

Thermosensitive membranes by radiation-induced graft polymerization of N-isopropyl acrylamide/acrylic acid on polypropylene nonwoven fabric  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was investigated on polypropylene nonwoven fabric to develop a thermosensitive material. The grafting was carried out using methanol, acetone and butanone as homopolymerization inhibitor in the reaction medium. Butanone was observed to give the maximum grafting. It was observed that the grafting is significantly influenced by the reaction conditions, such as radiation dose, monomer concentration, monomer ratio, solvent composition and reaction temperature. The degree of grafting increased as the AA and NIPAAm concentration in the reaction medium increased. The degree of grafting increased as the AA fraction in the NIPAAm/AA mixture increased. The temperature dependence of the grafting process is very much governed by the thermosensitive nature of the grafted chains right from the stage when initial grafting has taken place.

Ikram, Saiqa; Kumari, Mamta; Gupta, Bhuvanesh

2011-01-01

11

Graft copolymers of polyurethane with various vinyl monomers via radiation-induced miniemulsion polymerization: Influential factors to grafting efficiency and particle morphology  

Microsoft Academic Search

Graft copolymers of polyurethane (PU) with various vinyl monomers were synthesized through a one-pot but two-step miniemulsion polymerization process. Firstly, the polycondensation of isophorone diisocyanate (IPDI) with hydroxyl-terminated polybutadiene (HTPB) had been performed in aqueous miniemulsion at 40°C in order to obtain PU dispersions. Consecutively, an in-situ graft copolymerization of the vinyl monomers with the synthesized PU was initiated by

Hua Wang; Mozhen Wang; Xuewu Ge

2009-01-01

12

Adsorption of crude oil from aqueous solution by hydrogel of chitosan based polyacrylamide prepared by radiation induced graft polymerization.  

PubMed

The adsorption of crude oil (initial concentration 0.5-30 g/L) from aqueous solution using hydrogel of chitosan based polyacrylamide (PAM) prepared by radiation induced graft polymerization has been investigated. The prepared hydrogel was characterized by FTIR and SEM micrographs. The experiments were carried out as a function of different initial concentrations of oil residue, acrylamide concentration, contact time and pH to determine the optimum condition for the adsorption of residue oil from aqueous solution and sea water. The results obtained showed that the hydrogel prepared at concentration of 40% acrylamide (AAm) and at a radiation dose of 5 kGy has high removal efficiency of crude oil 2.3g/g at pH 3. Equilibrium studies have been carried out to determine the capacity of the hydrogel for adsorption of crude oil, Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherms constants. Equilibrium data were found to fit very well with both Freundlich and Langmuir models. Also the adsorption of oil onto the hydrogel behaves as a pseudo-second-order kinetic models rather than the pseudo-first-order kinetic model. PMID:21497016

Sokker, H H; El-Sawy, Naeem M; Hassan, M A; El-Anadouli, Bahgat E

2011-06-15

13

Simultaneous radiation induced graft polymerization of N-vinyl-2-pyrrolidone onto polypropylene non-woven fabric for improvement of blood compatibility  

NASA Astrophysics Data System (ADS)

In this study, N-vinyl-2-pyrrolidone (NVP) was grafted onto polypropylene non-woven fabric (PPNWF) through a simultaneous irradiation induced graft polymerization technique. Effect of the parameters of graft polymerization, i.e., monomer concentration, absorbed dose and dose rate, on the degree of grafting (DG) was investigated. The graft polymerization of NVP was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). A contact angle goniometry was used to test water contact angle (WCA) of original PPNWF and modified samples. The in vitro blood compatibility, including hemolysis, protein adsorption, platelet adhesion and activated partial thromboplastin time (APTT) of tested specimens, was evaluated. The results demonstrated that the hemocompatibility of PPNWF was improved via graft polymerization of NVP.

Li, Rong; Wang, Hengdong; Wang, Wenfeng; Ye, Yin

2013-07-01

14

Chemical Modification of Cellulose Nanofibrils by Graft Polymerization  

E-print Network

Chemical Modification of Cellulose Nanofibrils by Graft Polymerization Arie Mulyadi and Yulin Deng by UV-spectroscopy at 260 nm from PS absorbance of supernatant for case of graft polymerization hydrogen bond interaction Steric repulsion of grafted polymer Dispersion Quality in Nanocomposites

Das, Suman

15

High fluence irradiation effect on the ion beam graft polymerization method  

NASA Astrophysics Data System (ADS)

Radiation graft polymerization method has been applied to make many industrial product. Ion beam graft polymerization method has been developed by Betz and many researchers, and we have also developed the method with proton whose energy is below a few MeV. Using the method, the substrate, e.g. polyethylene film, is graft-polymerized and has the graft chains near the surface. To conduct the method for some times, the structure of graft chains near the surface can be formed. When we want to produce the graft chains inside of the substrate, the graft chains near the surface are unnecessary. One of our objectives is to produce a functional polymer with a structure in the film. When the sample is irradiated in sufficiently high fluence, the sample can't be graft-polymerized in the next irradiation. Comparing the density of radicals and the number of double bond with the degree of grafting, the reason why formation of a part not grafted in high fluence irradiation was discussed. Because the number of the double bond and the allyl radicals in PE are increased for high fluence irradiation, the number of the alkyl radical as a grafting point is decreased. Moreover, the alkyl radical is not produced in following irradiation since existence of double bond and peroxy radical.

Taniike, Akira; Hirooka, Yuya; Nakanishi, Noriaki; Nakamura, Raito; Furuyama, Yuichi

2014-07-01

16

Suspension Graft Polymerization of Methyl Methacrylate onto Selected Backbones  

Microsoft Academic Search

Methyl methacrylate was grafted onto poly(vinyl oxazoline ester) and poly(stearyl methacrylate) by a chain transfer suspension polymerization method to produce specialty polymeric products. These graft polymers should find application in powder coating, toner resin, and for encapsulating electronic components.

M. B. Amin; A. M. Usmani

1985-01-01

17

Graft polymerization of native chicken feathers for thermoplastic applications.  

PubMed

Inexpensive and biodegradable thermoplastics were developed through graft polymerization of native chicken feather with methyl acrylate as a potential substitute for petroleum products. Poultry feathers are available in large quantities at a low price. However, natural chicken feathers have poor thermoplasticity, cannot be used to develop thermoplastic products, have very limited industrial applications, and are often considered as solid wastes. In this research, the effects of graft polymerization conditions, such as molar ratio of NaHSO(3) to K(2)S(2)O(8), initiator and monomer concentrations, pH, temperature and time of polymerization, on grafting parameters, that is, the conversion of monomer to polymer, grafting percentage, and grafting efficiency were evaluated. Methyl acrylate was found to be successfully grafted onto functional groups on the surfaces of the chicken feathers, and optimal graft polymerization conditions were also obtained. The feather-g-poly(methyl acrylate) developed showed good thermoplasticity, and feather films had substantially higher tensile properties than soy protein isolate and starch acetate films. PMID:21302951

Jin, Enqi; Reddy, Narendra; Zhu, Zhifeng; Yang, Yiqi

2011-03-01

18

Radiation co-polymerization and its application in biotechnology  

E-print Network

The main results and achievements that have been done for the full duration of CRP reported as follows: (1) Radiation preparation of co-polymers, interpenetrating polymer networks and their applications in separation technology. (2) Preirradiation grafting co-polymerization of NIPAAm and other monomers on cotton cellulose fabric, silicone rubber etc and the discussion on mechanism. (3) UV-induced grafting and modification of polymers by high LET radiation.

HaHongFei; Yi Min; Zhai Mao Lin

1996-01-01

19

Crosslinked grafted PVC obtained by direct radiation grafting  

NASA Astrophysics Data System (ADS)

Direct radition-induced grafting of 4-vinylpyridine onto both pure and plasticized poly(vinyl chloride) has been studied. The effect of grafting conditions such as solvent, monomer concentration, irradiation dose, and inhibitor concentration on the grafting yield was investigated. The grafting process was enhanced by using distilled water as diluent and higher degrees of grafting were obtained as compared with other solvents used (benzene, methanol, and a mixture of methanol and water). The homopolymerization of 4-vinylpyridine was reduced to a minimum using ammonium ferrous sulfate and the suitable optimum concentration of the inhibitor was found to be 0.25 wt %. It was observed that the degrees of grafting onto plasticized PVC were higher than those onto pure one, at constant grafting conditions. The diffusibility of the monomer solution through the trunk polymers enhanced at higher monomer concentrations. The higher the monomer concentration the higher the degrees of grafting obtained. The dependence of the grafting rate on monomer concentration was found to be 0.15 and 0.4 order for the grafting onto pure and plasticized PVC films, respectively. The degree of grafting, at the higher irradiation doses, deviated from linearity and it tends to level off due to the recombination of some of the free radicals without initiating graft polymerization. Gel determination in the grafted films was investigated. The gel content in both grafted extracted pure and plasticized PVC films increased with the degree of grafting to reach a certain limiting values.

Hegazy, El-Sayed A.; Dessouki, Ahmed M.; El-Dessouky, Maher M.; El-Sawy, Naeem M.

20

Synthesis of Polymer Grafted Magnetite Nanoparticle with the Highest Grafting Density via Controlled Radical Polymerization  

PubMed Central

The surface-initiated ATRP of benzyl methacrylate, methyl methacrylate, and styrene from magnetite nanoparticle is investigated, without the use of sacrificial (free) initiator in solution. It is observed that the grafting density obtained is related to the polymerization kinetics, being higher for faster polymerizing monomer. The grafting density was found to be nearly 2 chains/nm2for the rapidly polymerizing benzyl methacrylate. In contrast, for the less rapidly polymerizing styrene, the grafting density was found to be nearly 0.7 chain/nm2. It is hypothesized that this could be due to the relative rates of surface-initiated polymerization versus conformational mobility of polymer chains anchored by one end to the surface. An amphiphilic diblock polymer based on 2-hydroxylethyl methacrylate is synthesized from the polystyrene monolayer. The homopolymer and block copolymer grafted MNs form stable dispersions in various solvents. In order to evaluate molecular weight of the polymer that was grafted on to the surface of the nanoparticles, it was degrafted suitably and subjected to gel permeation chromatography analysis. Thermogravimetric analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to confirm the grafting reaction. PMID:20596283

2009-01-01

21

Emulsion graft polymerization of 4-chloromethylstyrene on kenaf fiber by pre-irradiation method  

NASA Astrophysics Data System (ADS)

The stability of micelle size in 3% 4-chloromethylstyrene (CMS), 0.3% Tween 20 in water emulsion over time was studied using a static light scattering. It was found that the micelle diameter decreased with storage time and temperature. The influence of micelle size over time was then explored by adjusting the ratio of CMS to Tween 20 (10:1, 10:2, 10:4) at CMS concentration of 0.2-5.0%. It was found that the increase in average micelle diameter resulted in a decreased in the stability of CMS emulsion. Graft polymerization of CMS on kenaf fiber was carried out in emulsion with 350 nm micelle at various CMS concentrations at a dose of 150 kGy. It was found that the degree of grafting (Dg) was strongly dependent on the monomer concentration and time. However, the increase in micelles diameter from 250 nm to 500 nm resulted in the increased in Dg from 3% to 153%. This extraordinary result led us to investigate the micelle size distributions of CMS emulsion during graft polymerization. It was found that the diameter of micelle decreased rapidly to 100 nm within 2 h. It was discovered from digital photomicrography the existence of multiple emulsions in the CMS emulsion. It was proposed that the enhancement of grafting yield is governed by emulsion breakdown mechanisms through radical effect during radiation induced graft polymerization.

Mohamed, Nor Hasimah; Tamada, Masao; Ueki, Yuji; Seko, Noriaki

2013-01-01

22

Improvement of the polymer stability by radiation grafting  

NASA Astrophysics Data System (ADS)

Losses of the stabilizer due to extractability or volatility immediately affect the ultimate performance of polymer products. A new approach to increase the persistence of the stabilizer in the final product is to chemically bind it to the polymer backbone. Radiation grafting or crosslinking could be an efficient method for this, when the stabilizer is polymerizable. By a mutual gamma irradiation method photoprotector 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone has been readily grafted to low-density polyethylene in benzene, tetrahydrofuran and methanol solution, respectively. Surface grafting occurs in a methanol solution of stabilizer, while in benzene and tetrahydrofuran solutions of the stabilizer, grafting proceeds more or less in the inner parts of the polymeric film as well. UV stability tests and changes in the mechanical properties of artificially and naturally aged films indicate pronounced protective effect achieved by the grafted stabilizer. Surface grafting is an efficient photostabilization method since the grafted stabilizer is chemically bound to a polymeric surface and in this way the problem of evaporation of blended stabilizers during the prolonged use of polymeric materials is eliminated.

Ranogajec, F.; Mlinac-Mišak, M.

2004-09-01

23

Surface modification of polypropylene membrane by polyethylene glycol graft polymerization.  

PubMed

Polypropylene hollow fiber microporous membranes have been used in a wide range of applications, including blood oxygenator. The hydrophobic feature of the polypropylene surface causes membrane fouling. To minimize fouling, a modification consisting of three steps: surface activation in H2 and O2 plasma, membrane immersion in polyethylene glycol (PEG) and plasma graft polymerization was performed. The membranes were characterized by contact angle measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Oxygen transfer of modified membranes was also tested. The stability of grafted PEG was measured in water and in phosphate buffer saline (PBS) at 37°C. Blood compatibility of modified surfaces was evaluated by the platelet adhesion method. Water contact angel reduction from 110° to 72° demonstrates the enhanced hydrophilicity, and XPS results verify the presence of oxygenated functional groups due to the peak existence in 286 eV as a result of PEG grafting. The results clearly indicate that plasma graft-polymerization of PEG is an effective way for antifouling improvement of polypropylene membranes. Also, the results show that oxygen transfer changes in PEG grafted membranes are not significant. PMID:25063140

Abednejad, Atiye Sadat; Amoabediny, Ghasem; Ghaee, Azadeh

2014-09-01

24

Durable Nanolayer Graft Polymerization of Functional Finishes Using Atmospheric Plasma  

NASA Astrophysics Data System (ADS)

Various applications of atmospheric pressure plasma were investigated in conjunction with different chemistries on nonwoven materials including spunbond polyester (PET) and spunbod polypropylene for fuel separation and antimicrobial functionalities. Hydrophobic/Oleophobic properties were conferred on nonwoven polyester (PET) via plasma-induced graft polymerization of different hydrophobic non-C8 perfluorocarbon chemistry including perfluorohexylethylmethacrylate, perfluorohexylethylacrylate, allylpentafluorobenzene, pentafluorostyrene, or 1,3-divinyltetramethyldisiloxane in the vapor form using both in-situ and down-stream plasma configurations. Different nanolayers of the grafted polymer were furnished on nonwovens to generate surfaces with different level of wettabilities for medical applications and water/fuel separation. The effect of various hydrophobic chemistry, different plasma conditions, and plasma device parameters including plasma power and plasma exposure time were studied and the performance was characterized by measuring the contact angle and the wettability rating against liquids with broad range of surface tensions. Vapor deposition of 2-(perfluorohexyl)ethyl methacrylate and pentafluorostyrene on nonwoven PET followed by plasma-induced graft polymerization was investigated for possible use in water/fuel separation. Different nanolayer thicknesses (80-180nm) of the grafted polymer were achieved to generate surfaces with different wettabilities for water/fuel separation of different fuel compositions. The effect of different plasma conditions and device parameters including the flow rate of monomers, power of the device, and time of plasma exposure on the separation of different fuels was studied and characterized by measuring the surface energy of the treated substrates. The surface chemistry and morphology of the treated samples were characterized using XPS, SEM and TOF-SIMS techniques which confirmed the grafting of monomer onto the substrate. Furthermore, spunbond nonwoven polypropylene fabric, commonly used for hygienic products, was treated with diallyldimethylammonium chloride (DADMAC). Atmospheric pressure glow discharge plasma was used to induce free radical chain polymerization of the ADMAC monomer, which conferred a graft polymerized network on the fabric with durable antimicrobial properties. The effect of different DADMAC concentration, and plasma conditions including the RF power and the time of plasma exposure were studied and the optimum treatment conditions were identified by calculating the surface charge density on the treated fabrics. The presence of poly-DADMAC on the polypropylene surface was confirmed using SEM, FT-IR and TOF-SIMS. Antibacterial performance was investigated using standard test methods (AATCC TM 100) for both gram positive and gram negative bacteria. The antimicrobial results showed 6 log reductions in the bacterial activities of K. pneumoniae and S .aureus, which was unprecedented using a plasma-induced graft polymerization approach.

Mazloumpour, Maryam

25

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10.sup.15 to 10.sup.21 molecules of dopant/cm.sup.3. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, Jr., Charles (Albuquerque, NM); Hughes, Robert C. (Albuquerque, NM); Kepler, R. Glen (Albuquerque, NM); Kurtz, Steven R. (Albuquerque, NM)

1986-01-01

26

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10/sup 15/ to 10/sup 21/ molecules of dopant/cm/sup 3/. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, C. Jr.; Hughes, R.C.; Kepler, R.G.; Kurtz, S.R.

1984-07-16

27

Polymer brush gradients grafted from plasma-polymerized surfaces.  

PubMed

A new method for generating a surface density gradient of polymer chains is presented. A substrate-independent polymer deposition technique was used to coat materials with a chemical gradient based on plasma copolymerization of 1,7-octadiene and allylamine. This provided a uniform chemical gradient to which initiators for atom transfer radical polymerization (ATRP) were immobilized. After surface-initiated atom transfer radical polymerization (SI-ATRP), poly(2-hydroxyethyl methacrylate) (PHEMA) chains were grafted from the surface and the measured thickness profiles provided direct evidence for how surface crowding provides an entropic driving force resulting in chain extension away from the surface. Film thicknesses were found to increase with the position along the gradient surface, reflecting the gradual transition from collapsed to more extended surface-tethered polymer chains as the grafting density increased. The method described is novel in that the approach provides covalent linkages from the polymer coating to the substrate and is not limited to a particular surface chemistry of the starting material. PMID:24967529

Coad, Bryan R; Bilgic, Tugba; Klok, Harm-Anton

2014-07-22

28

Inorganic Surface Nanostructuring by Atmospheric Pressure Plasma-Induced Graft Polymerization  

E-print Network

by graft polymerization in both N-methyl-2-pyrrolidone (NMP) and in an NMP/water solvent mixture in pure NMP resulted in a polymer feature spacing of as low as 5-10 nm (average feature diameter of about of 5.5 nm. Graft polymerization in an NMP/water solvent mixture, however, resulted in polymer feature

Hicks, Robert F.

29

Studies on the graft polymerizations of styrene and methyl methacrylate to hydroxyl terminated polybutadiene  

Microsoft Academic Search

Hydroxyl terminated Polybutadiene (HTPB) was grafted with styrene (St) or methyl methacrylate (MMA) by free radical solution polymerization. The graft copolymerizations were conducted in benzene at 70 °C. The initiators used were benzoyl peroxide (BPO) and azobis-isobutyronitrile (AIBN). The microstructures of theobtained graft copolymers were characterized by13C NMR measurement and the DEPT technique, as well as by IR spectrometer. The

Chang-Tay Lin; Mon-Chun Liu

1995-01-01

30

Optical dispersion of radiation-grafted fluoro-polymer.  

PubMed

Controlling the index of refraction of polymers plays an important role in their advanced nonlinear optical and electro-optical applications as well as in nanophotonics and biophotonic technologies. A radiation-induced grafting of acrylic acid (AAc) onto poly(tetrafluoroethylene-co-perfluorovinyl ether) (PFA) copolymer films was carried out to synthesize graft copolymer films using gamma-irradiation by the mutual method. The resulted films were characterized by Fourier transform infrared spectroscopy. The grafting process is associated with cross-linking through which a considerable change in the material refractive index is achieved. The linear refractive index, optical dispersion, and the quantum parameters of grafted poly(tetrafluoroethylene-co-perfluorovinyl ether) (PFA-g-PAAc) polymeric film are determined in a wide spectral range of 0.2-3 microm. The wavelength for zero material dispersion is evaluated. The oscillator, dispersion, and lattice energies, respectively, are calculated revealing the optical properties of the studied trunk polymeric substrate and the grafted ones. The origin of the optical properties has been discussed. PMID:18404177

El-Diasty, Fouad; El-Sawy, N M

2008-04-10

31

Radiation-Induced Grafting on Polyamides.  

National Technical Information Service (NTIS)

The objective of the project was to investigate radiation-induced grafting on polyamides, with emphasis on fluorine-containg vinyl monomers. The principal experimental technique was the gamma ray irradiation of polyamide film samples immersed in suitable ...

J. E. Wilson

1972-01-01

32

Graft-Copolymerization onto Carbon Black.  

National Technical Information Service (NTIS)

Radiation-induced graft copolymerization of vinyl monomer onto carbon black was performed. During the gamma -ray- and electron beam-induced polymerization (In-source), or the electron beam post-polymerization, the graft-copolymerization behavior was affec...

Y. Nakase, M. Nishii, T. Kijima, H. Kato

1988-01-01

33

Polymer-grafted nanoparticles prepared by surface-initiated polymerization: the characterization of polymer chain conformation, grafting density and polydispersity correlated to the grafting surface curvature.  

PubMed

The polymer-grafted nanoparticles prepared by the surface-initiated polymerization induced from the spherical surface is studied by coarse-grained molecular dynamics simulations combined with the stochastic reaction model. The coupling effect of the initiator density and the grafting surface curvature is mainly investigated. The confinement degree greatly changes with the grafting surface curvature, thus the initiation efficiency, the grafted chain polydispersity, as well as the chain mass distribution show great dependence on the surface curvature. The results reveal that preparing the nanoparticle with desired size (i.e., grafting surface curvature) is crucial for control of the grafted chain polydispersity and even its dispersion in the polymer matrix. Our studies shed light on better design of grafted nanoparticles and better control of dispersion in polymer matrices for improving the performance of polymer nanocomposite materials. PMID:23928871

Xue, Yao-Hong; Zhu, You-Liang; Quan, Wei; Qu, Fu-Heng; Han, Cheng; Fan, Jing-Tao; Liu, Hong

2013-10-01

34

Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization  

NASA Astrophysics Data System (ADS)

In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

Li, Zhi; Zhang, Wei; Wang, Xinwei; Mai, Yongyi; Zhang, Yumei

2011-06-01

35

Study and Optimization on graft polymerization under normal pressure and air atmospheric conditions, and its application to metal adsorbent  

NASA Astrophysics Data System (ADS)

Radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene (NWPE) fabric was achieved under normal pressure and air atmospheric conditions, without using unique apparatus such as glass ampoules or vacuum lines. To attain graft polymerization under normal pressure and air atmospheric conditions, the effects of the pre-irradiation dose, pre-irradiation atmosphere, pre-irradiation temperature, de-aeration of GMA-emulsion, grafting atmosphere in a reactor, and dissolved oxygen (DO) concentration in GMA-emulsion on the degree of grafting (Dg) were investigated in detail. It was found that the DO concentration had the strongest influence, the pre-irradiation dose, de-aeration of emulsion and grafting atmosphere had a relatively strong impact, and the pre-irradiation atmosphere and pre-irradiation temperature had the least effect on Dg. The optimum DO concentration before grafting was 2.0 mg/L or less. When a polyethylene bottle was used as a reactor instead of a glass ampoule, graft polymerization under normal pressure and air atmospheric conditions could be achieved under the following conditions; the pre-irradiation dose was more than 50 kGy, the volume ratio of GMA-emulsion to air was 50:1 or less, and the DO concentration in GMA-emulsion during grafting was below 2.0 mg/L. Under these grafting conditions, Dg was controlled within a range of up to 362%. The prepared GMA-grafted NWPE (GMA-g-NWPE) fabric was modified with a phosphoric acid to obtain an adsorbent for heavy metal ions. In the column-mode adsorption tests of Pb(II), the adsorption performance of the produced phosphorylated GMA-g-NWPE fabric (fibrous metal adsorbent) was not essentially dependent on the flow rate of the feed. The breakthrough points of 200, 500, and 1000 h-1 in space velocity were 483, 477 and 462 bed volumes, and the breakthrough capacities of the three flow rates were 1.16, 1.15 and 1.16 mmol-Pb(II)/g-adsorbent.

Ueki, Yuji; Chandra Dafader, Nirmal; Hoshina, Hiroyuki; Seko, Noriaki; Tamada, Masao

2012-07-01

36

The synthesis of well-defined poly(vinylbenzyl chloride)-grafted nanoparticles via RAFT polymerization  

PubMed Central

Summary We describe the use of one of the most advanced radical polymerization techniques, the reversible addition fragmentation chain transfer (RAFT) process, to produce highly functional core–shell particles based on a silica core and a shell made of functional polymeric chains with very well controlled structure. The versatility of RAFT polymerization is illustrated by the control of the polymerization of vinylbenzyl chloride (VBC), a highly functional monomer, with the aim of designing silica core–poly(VBC) shell nanoparticles. Optimal conditions for the control of VBC polymerization by RAFT are first established, followed by the use of the “grafting from” method to yield polymeric brushes that form a well-defined shell surrounding the silica core. We obtain particles that are monodisperse in size, and we demonstrate that the exceptional control over their dimensions is achieved by careful tailoring the conditions of the radical polymerization. PMID:23843918

Moraes, John; Ohno, Kohji; Gody, Guillaume; Maschmeyer, Thomas

2013-01-01

37

Self-organization of dipeptide-grafted polymeric nanoparticles film: A novel method for surface modification  

Microsoft Academic Search

Novel dipeptide-grafted polymeric nanoparticles were prepared by grafting the dipeptide (Gly-Gly) to a block copolymer backbone, comprised of styrene-alt-(maleic anhydride) and styrene. In aqueous solution PSt130-b-P(St-alt-MAn)58-g-GlyGly26 formed stable dispersed spherical aggregates of ca. 75nm. The critical micelle concentration for the dipeptide-grafted block copolymer self-aggregates was 6.3×10?3mgmL?1. The zeta-potential of the aggregates was estimated experimentally. The dispersed polymer nanoparticles effectively self-organized

Jingtian Han; Patrick Silcock; A. James McQuillan; Phil Bremer

2010-01-01

38

Radiation sterilization of polymeric implant materials  

SciTech Connect

High-energy irradiation sterilization of medical devices and implants composed of polymeric biomaterials that are in contact with tissue and/or blood, may adversely affect their long-term mechanical and/or biological performance (tissue and/or blood compatibility). Since many polymeric implants may contain trace quantities of catalysts and/or other additives, the effect of high-energy radiation on these additives, and possible synergistic effects with the polymer chains under the influence of high-energy radiation, must be considered. It is essential to indicate whether polymeric implants are used in short-term (acute) or long-term (chronic) applications. Relatively small changes in their physicochemical, mechanical, and biological properties may be tolerable in the short term, whereas similar changes may lead to catastrophic failures in long-term applications. Therefore, polymeric implants which are to be sterilized by high-energy irradiation should be carefully evaluated for long-term property changes which may be induced by the radiation.

Bruck, S.D.; Mueller, E.P.

1988-08-01

39

Preparation of degradable polymeric nanocapsules from hyperbranched poly (amine ester) grafted nanosilica templates.  

PubMed

A facile approach for the preparation of degradable crosslinked polymeric nanocapsules with hydroxyl functional groups was developed by polycondensation from the nanosilica templates. The hyperbranched poly (amine ester) grafted silica nanoparticles (SN-HPAE) were crosslinked with hexamethylene diisocyanate (HDI). Then the silica templates were removed by HF etching to produce the degradable polymeric nanocapsules. The inner diameter of polymeric nanocapsules is in the range of 20-100 nm, which is characterised by transmission electron microscopy (TEM). The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis and TEM. PMID:20499996

Shen, R; Mu, B; Wang, W; Du, P; Liu, P

2010-06-01

40

The Synthesis of Cellulose Graft Copolymers Using Cu(0)-Mediated Polymerization  

NASA Astrophysics Data System (ADS)

Cellulose is the most abundant renewable polymer on the planet and there is great interest in expanding its use beyond its traditional applications. However, its hydrophilicity and insolubility in most common solvent systems are obstacles to its widespread use in advanced materials. One way to counteract this is to attach hydrophobic polymer chains to cellulose: this allows the properties of the copolymer to be tailored by the molecular weight, density, and physical properties of the grafts. Two methods were used here to synthesize the graft copolymers: a 'grafting-from' approach, where synthetic chains were grown outward from bromoester moieties on cellulose (Cell-BiB) via Cu(0)-mediated polymerization; and a 'grafting-to' approach, where fully formed synthetic chains with terminal sulfide functionality were added to cellulose acetate with methacrylate functionality (CA-MAA) via thiol-ene Michael addition. The Cell-BiB was synthesized in the ionic liquid 1-butyl-3-methylimidazolium chloride and had a degree of substitution of 1.13. Polymerization from Cell-BiB proceeded at similar but slightly slower rate than an analogous non-polymeric initiator (EBiB). The average graft density of poly(methyl acrylate) chains was 0.71 chains/ring, with a maximum of 1.0 obtained. The graft density when grafting poly(methyl methacrylate) was only 0.15, and this appeared to be due to the slow initiation of BiB groups. Using EBiB to model the reaction and improve the design should allow this to be overcome. Chain extension experiments demonstrated the living behaviour of the polymer. The CA-MAA was synthesized by esterification with methacrylic acid. Reactions of CA-MAA with thiophenol and dodecanethiol resulted in quantitative addition of the thiol to the alkene. The grafts were synthesized by Cu(0)-mediated polymerization from a bifunctional initiator containing a disulfide bond, followed by reduction to sulfides. The synthetic polymers were successfully grafted to CA-MAA but the grafting yield was limited by the low sulfide functionality. Better retention of sulfide functionality is necessary for more efficient grafting.

Donaldson, Jason L.

41

Technique of radiation polymerization in fine art conservation: a potentially new method of restoration and preservation. [Uv and electron beams  

SciTech Connect

The technique of using radiation polymerization for the restoration and preservation of art treasures is considered. The processes discussed include both radiation grafting and rapid cure procedures, particularly reactions initiated by uv and eb. Representative examples where the technique has already been used are treated including typical applications with paintings, tapestries, leather and archival repair. The structure of the monomers and oligomers used in both grafting and rapid cure systems is outlined. The experimental conditions where grafting may occur during radiation rapid cure processing are discussed. Possible future developments of the technique are outlined. 1 figure, 8 tables.

Garnett, J.L. (Univ. of New South Wales, Kensington, Australia); Major, G.

1982-01-01

42

Graft polymerization and plasma treatment of polymer membranes for fouling reduction: A review  

Microsoft Academic Search

This article presents a review of recent developments in surface modification of polymer membranes via graft polymerization and plasma treatment for reduction of fouling with organic compounds and microorganisms in pressure driven membrane processes. The factors affecting membrane fouling, such as membrane hydrophilicity, charge and surface roughness are discussed. The recent studies in which the reduction of organic fouling and

Victor M. Kochkodan; Virender K. Sharma

2012-01-01

43

Radiation-induced grafting of diallyldimethylammonium chloride onto acrylic acid grafted polyethylene  

NASA Astrophysics Data System (ADS)

Diallyldimethylammonium chloride (DADMAC) was grafted onto polyethylene (PE) films by a double grafting procedure. The PE film was initially modified by grafting acrylic acid (AA), through a mutual irradiation method. AA-g-PE film, thus obtained was subjected to subsequent radiation grafting reaction of DADMAC, to give a DADMAC-g-AA-g-PE film having a comb-type structure. The influence of different conditions, such as the extent of AA grafting, DADMAC concentration, absorbed dose and dose rate, on the grafting yield of DADMAC was investigated. A maximum DADMAC grafting of 30% was achieved. The equilibrium degree of swelling (EDS) of the grafted films were gravimetrically determined. TGA and FT-IR techniques were employed to characterize the grafted PE films.

Francis, Sanju; Dhanawade, B. R.; Mitra, D.; Varshney, Lalit; Sabharwal, Sunil

2009-01-01

44

Technique of radiation polymerization in fine art conservation: a potentially new method of restoration and preservation. [Uv and electron beams  

Microsoft Academic Search

The technique of using radiation polymerization for the restoration and preservation of art treasures is considered. The processes discussed include both radiation grafting and rapid cure procedures, particularly reactions initiated by uv and eb. Representative examples where the technique has already been used are treated including typical applications with paintings, tapestries, leather and archival repair. The structure of the monomers

J. L. Garnett; G. Major

1982-01-01

45

Radiation grafting of N,N?-dimethylacrylamide and 2-hydroxyethylmethacrylate onto polypropylene films by one step method  

NASA Astrophysics Data System (ADS)

The work presented herein reports on polypropylene films grafted with N,N'-dimethylacrylamide and 2-hydroxyethylmethacrylate. The grafted films were obtained by an oxidative pre-irradiation method in one step using a gamma source of 60Co. The optimal conditions such as reaction time, monomer concentrations and radiation doses were investigated. Characterization of the grafted polymers was carried out through FTIR-ATR, TGA, DSC, and swelling. Grafts onto polymeric films between 10 and 850% were obtained at doses from 20 to 150 kGy and a dose rate of 8.3 kGy/h.

Morales-Wiemer, E. A.; Macossay, J.; Bucio, E.

2013-03-01

46

Preparation of hollow-fiber membranes by plasma-graft filling polymerization for organic-liquid separation  

Microsoft Academic Search

Filling-type hollow-fiber membranes for separating organic-liquid mixtures were prepared by plasma-graft polymerization technique using porous hollow-fiber substrates. Methyl acrylate (MA) was used as the grafting monomer. From analyses with scanning electron microscope (SEM), optical microscope, XPS imaging and micro FT-IR, it was confirmed that grafted polymer filled the pores of the hollow-fiber substrates and the thickness of this grafted layer

Teruhiko Kai; Toshinori Tsuru; Shin-ichi Nakao; Shoji Kimura

2000-01-01

47

Radiation-induced grafting of chlorinated PVC for preparation of plastic foams  

NASA Astrophysics Data System (ADS)

Graft products of chlorinated PVC with styrene were prepared by a radiation-grafting method using 60Co- ?-ray source. The aim was the preparation of foamed plastics by applying the traditional polystyrene foaming method. Two types of chlorinated PVC (PVCC) were used: radiation-chlorinated PVC, made by the fluidized-bed chlorination process, and solution-chlorinated PVC. Both of the PVCC types were grafted with styrene without any difficulty. The required particle size for an effective foaming was obtained by extrusion and granulation of the grafted powder. The foaming processes are quite different: graft products on the basis of solution-chlorinated PVC lead to plastic foams with a density lower than 0.1 g/cm 3 whereas those prepared from solid-chlorinated PVC result in foams with much higher density (Friese, K, Tannert, F, 1990. Proceedings of the 7th Tihany Symposium on Radiation Chemistry, p. 367). Solid-chlorinated PVC is foamable with pentane, after compounding it with polymeric modifiers. Grafting of granules on the basis of such compounds increases the content of pentane, as well as the foaming rate. The foamed graft polymers are non-inflammable and self-extinguishing.

Friese, K.; Tannert, F.

1999-06-01

48

DFT study of the ring opening polymerization of ?-caprolactone by grafted lanthanide complexes: 1--Effect of the grafting mode on the reactivity of borohydride complexes.  

PubMed

The influence of the grafting mode of a borohydride lanthanum complex on a silica surface on the energetic (kinetic and thermodynamic parameters) of the Ring Opening Polymerization (ROP) reaction of ?-caprolactone has been studied in the framework of density functional theory (DFT). For all considered grafted catalysts (monografted, bigrafted, or bigrafted after breaking of a Si-O-Si bridge), it is shown that lanthanum borohydride grafted complexes are efficient in lactone polymerization. Moreover, the reaction pathways (leading to a -CH(2) OBH(2) chain end) are predicted to be energetically similar for the three grafting modes, indicating that all grafted modes can account for the activity for silica treated at 700 °C. The catalytic activity of the grafted complexes is also very similar to that of the homogeneous complexes. PMID:21935526

Del Rosal, Iker; Poteau, Romuald; Maron, Laurent

2011-11-14

49

R&D for graft adsorbents by radiation processing  

NASA Astrophysics Data System (ADS)

Fibrous adsorbent for removal and recovery of metal ions have been synthesized by graft polymerization. In the grafting, the functional groups which have high selectivity against for target metal ions such as Fe, Sc, As, and U are introduced onto nonwoven fabric. When the monomer has a chelate group which makes selective coordination bond to specific these ions, it was directly grafted on the trunk polymer. In the case of precursor monomer having functional groups such as epoxy ring, the grafted trunk fabric is chemically modified. The resultant fibrous adsorbent leads the swift adsorption of metal ions. This property by using fibrous material can reduce the column size of adsorbent in the purification of waste water. The size of purification equipment becomes quite compact and that implies total volume of equipment can reduce. Instead of organic solvent, emulsion system which disperses monomer micelles in water with assistance of surfactant was found to accelerate the graft polymerization. This means the air pollution from organic solvent can be avoided by water system grafting. Furthermore, since the emulsion grafting was highly efficient, the required irradiation dose was considerably lower compared to general organic solvent system. As a result, the emulsion grafting has enormous potential for natural polymer to use as a trunk material for grafting. If a natural polymer such as cellulose can be used, the dependence on petroleum resources, the amount of industrial waste and the generation of carbon dioxide will be reduced to some extent.

Seko, Noriaki; Tamada, Masao

50

The role of multifunctional acrylates in radiation grafting and curing reactions  

NASA Astrophysics Data System (ADS)

Multifunctional acrylates (MFAs) are used extensively in radiation rapid cure (RRC) formulations involving u.v. and EB processing to achieve fast rates of polymerization and cross-linking if required. For certain RRC applications, the ability to achieve concurrent grafting with cure can lead to improved properties of the finished product. In the current work the effect of MFAs on concurrent grafting during the curing process is evaluated from a basic study of the role of these MFAs on a typical grafting reaction initiated by u.v. or ionizing radiation. The model used for the grafting work was the copolymerization of styren to the polyolefins and cellulose. It is found that the presence of the MFA and related polyfunctional monomers (PFMs) in additive amounts in the styrene grafting solution enhances the copolymerization yield under certain radiation conditions. Synergistic effects of the MFAs and PFMs with other additives such as mineral acids, inorganic salts (e.g. lithium perchlorate) and specific organic compounds (e.g. urea) were observed in the model grafting reactions. When additives such as silanes and fluorinated alkyl esters, which are important in RRC formulations to achieve slip and flow in the cured film, are incorporated into the model grafting monomer solution, the former additive retards copolymerization whereas the latter enhances it. The inclusion of MFAs in these monomer solutions leads to large increases in graft with both silanes and fluorinated alkyl esters. The result implies that MFAs, in addition to speeding cure and cross-linking in RRC processes, may also enhance adhesion to certain substrates because of an increase in concurent grafting during cure. A mechanism for these additive effects in concurrent grafting and curing is proposed.

Dworjanyn, Paul A.; Garnett, John L.

51

Grafting of molecularly imprinted polymer to porous polyethylene filtration membranes by plasma polymerization.  

PubMed

An application of plasma-induced grafting of polyethylene membranes with a thin layer of molecularly imprinted polymer (MIP) was presented. High-density polyethylene (HDPE) membranes, "Vyon," were used as a substrate for plasma grafting modification. The herbicide atrazine, one of the most popular targets of the molecular imprinting, was chosen as a template. The parameters of the plasma treatment were optimized in order to achieve a good balance between polymerization and ablation processes. Modified HDPE membranes were characterized, and the presence of the grafted polymeric layer was confirmed based on the observed weight gain, pore size measurements, and infrared spectrometry. Since there was no significant change in the porosity of the modified membranes, it was assumed that only a thin layer of the polymer was introduced on the surface. The experiments on the re-binding of the template atrazine to the membranes modified with MIP and blank polymers were performed. HDPE membranes which were grafted with polymer using continuous plasma polymerization demonstrated the best result which was expressed in an imprinted factor equal to 3, suggesting that molecular imprinting was successfully achieved. PMID:23748644

Cowieson, D; Piletska, E; Moczko, E; Piletsky, S

2013-08-01

52

Enhanced Polymer Grafting from Multiwalled Carbon Nanotubes through Living Anionic Surface-Initiated Polymerization.  

SciTech Connect

Anionic surface-initiated polymerization of ethylene oxide and styrene has been performed using multiwalled carbon nanotubes (MWNTs) functionalized with anionic initiators. The surface of MWNTs was modified via covalent attachment of precursor anions such as 4-hydroxyethyl benzocyclobutene (BCBEO) and 1-benzocyclobutene-1 -phenylethylene (BCB-PE) through Diels-Alder cycloaddition at 235 C. Surface-functionalized MWNTs-g-(BCB-EO)n and MWNTs-g-(BCB-PE)n with 23 and 54 wt % precursor initiators, respectively, were used for the polymerizations. Alkoxide anion on the surface of MWNTs-g-(BCB-EO)n was generated through reaction with potassium triphenylmethane for the polymerization of ethylene oxide in tetrahydrofuran and phenyl substituted alkyllithium was generated from the surface of MWNTs-g-(BCB-PE)n using sec-butyllithium for the polymerization of styrene in benzene. In both cases, the initiation was found to be very slow because of the heterogeneous reaction medium. However, the MWNTs gradually dispersed in the reaction medium during the polymerization. A pale green color was noticed in the case of ethylene oxide polymerization and the color of initiator as well as the propagating anions was not discernible visually in styrene polymerization. Polymer grafted nanocomposites, MWNTs-g-(BCB-PEO)n and MWNTs-g-(BCB-PS)n containing a very high percentage of hairy polymer with a small fraction of MWNTs (<1 wt %) were obtained. The conversion of ethylene oxide and the weight percent of PEO on the surface of the MWNTs increased with increasing reaction time indicating a controlled polymerization. The polymer-grafted MWNTs were characterized using FTIR, 1H NMR, Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy (TEM). Size exclusion chromatography of the polymer grafted MWNTs revealed broad molecular weight distributions (1.3 < Mw/Mn < 1.8) indicating the presence of different sizes of polymer nanocomposites. The TEM images showed the presence of thick layers of polymer up to 30 nm around the MWNTs. The living nature of the growing polystyryllithium was used to produce diblock copolymer grafts using sequential polymerization of isoprene on the surface of MWNTs.

Sakellariou, Georgios [ORNL; Ji, Haining [ORNL; Mays, Jimmy [ORNL; Baskaran, Durairaj [University of Tennessee, Knoxville (UTK)

2008-01-01

53

Radiation grafting of styrene on starch with high efficiency  

NASA Astrophysics Data System (ADS)

Wheat starch grafted with polystyrene (PS-g-starch) was synthesized via polymerization grafting of styrene on starch by gamma-ray. The effects of starch/styrene weight ratio, and amount of applied doses (5-40 kGy) on the percentage of grafting, G (%), were investigated. The results showed that G (%) increased with increasing starch content. The optimum condition, starch/styrene weight ratio 1/3 and the applied dose 10 kGy, led to 252.9% of grafting. The obtained graft copolymer was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, and scanning electron microscopy. FTIR spectroscopy as well as the XRD analysis exhibited the changes in chemical and crystalline structure of starch after grafting reaction. TGA demonstrated the changes in thermal stability of PS-g-starch copolymer. SEM micrographs indicated porous patches of PS adhering on the starch.

Sheikh, N.; Akhavan, A.; Ataeivarjovi, E.

2013-04-01

54

The effects of early postoperative radiation on vascularized bone grafts  

SciTech Connect

The effects of early postoperative radiation were assessed in free nonvascularized and free vascularized rib grafts in the canine model. The mandibles of one-half of the dogs were exposed to a cobalt 60 radiation dose of 4080 cGy over a 4-week period, starting 2 weeks postoperatively. The patency of vascularized grafts was confirmed with bone scintigraphy. Histological studies, including ultraviolet microscopy with trifluorochrome labeling, and histomorphometric analyses were performed. Osteocytes persist within the cortex of the vascularized nonradiated grafts to a much greater extent than in nonvascularized, nonradiated grafts. Cortical osteocytes do not persist in either vascularized or nonvascularized grafts subjected to radiation. New bone formation is significantly retarded in radiated grafts compared with nonradiated grafts. Periosteum and endosteum remained viable in the radiated vascularized grafts, producing both bone union and increased bone turnover, neither of which were evident to any significant extent in nonvascularized grafts. Bone union was achieved in vascularized and non-vascularized nonradiated bone. In the radiated group of dogs, union was only seen in the vascularized bone grafts.

Evans, H.B.; Brown, S.; Hurst, L.N. (Division of Plastic and Reconstructive Surgery, University of Western Ontario, London (Canada))

1991-06-01

55

Graft polymerization and other methods to reduce the hygroscopic nature of cellulose insulation  

SciTech Connect

Cellulosic insulation materials are widely used in power transformers and other high voltage devices, but require intensive drying out to remove all moisture. This paper describes three methods used to modify cellulose to reduce its hygroscopicity, of which graft polymerization was the most successful method. The modified paper sheets, however, lost some mechanical strength properties, and showed a tendency to be thicker than the starting material.

Oommen, T.V. [ABB Transmission Technology Inst., Raleigh, NC (United States); Andrady, T.L. [Research Triangle Inst., Research Triangle Park, NC (United States). Camille Dreyfus Lab.

1996-12-31

56

Radical graft polymerization from carbon whisker initiated by peroxyester groups introduced onto the surface  

Microsoft Academic Search

The radical graft polymerization of vinyl monomers onto carbon whiskers, i.e. vapor grown carbon fibers, initiated by tert-butyl peroxyester groups that are introduced onto the surface was investigated. The introduction of tert-butyl peroxyester groups onto the carbon whisker surface was achieved by the reaction of acyl chloride groups on the surface with tert-butyl hydroperoxide. The carbon whisker having acyl chloride

Hiroshi Ueno; Norio Tsubokawa

1995-01-01

57

Grafting amphiphilic brushes onto halloysite nanotubes via a living RAFT polymerization and their Pickering emulsification behavior.  

PubMed

Amphiphilic brushes of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) are grafted onto halloysite nanotubes (HNTs) via a surface reversible addition-fragmentation chain transfer (RAFT) living polymerization through anchoring R group in RAFT agent S-1-dodecyl-S'-(R,R'-dimethyl-R?-acetic acid) trithiocarbonates (DDMAT). The characterization of TGA, TEM, and GPC show that amphiphilic brushes are successfully grafted onto HNTs in a living manner. To verify the amphiphilicity of HNTs grafted with block copolymers, their Pickering emulsification behavior in water/soybean oil diphase mixture is studied. The results show that modified HNTs can emulsify water/soybean oil diphase mixture and the emulsification performance is dependent on microstructure of amphiphilic brushes such as hydrophilic/hydrophobic segment size and sequence. PMID:24494662

Hou, Yifan; Jiang, Junqing; Li, Kai; Zhang, Yanwu; Liu, Jindun

2014-02-20

58

Temperature responsive cellulose-graft-copolymers via cellulose functionalization in an ionic liquid and RAFT polymerization.  

PubMed

Well-defined cellulose-graft-polyacrylamide copolymers were synthesized in a grafting-from approach by reversible addition-fragmentation chain transfer polymerization (RAFT). A chlorine moiety (degree of substitution DS(Cl) ? 1.0) was introduced into the cellulose using 1-butyl-3-methylimidazolium chloride (BMIMCl) as solvent before being substituted by a trithiocarbonate moiety resulting in cellulose macro-chain transfer agents (cellulose-CTA) with DS(RAFT) of 0.26 and 0.41. Poly(N,N-diethylacrylamide) (PDEAAm) and poly(N-isopropylacrylamide) (PNIPAM) were subsequently grafted from these cellulose-CTAs and the polymerization kinetics, the molecular weight characteristics and the product composition were studied by nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and size exclusion chromatography of the polyacrylamides after cleavage from the cellulose chains. The number-average molecular weights, Mn, of the cleaved polymers ranged from 1100 to 1600 g mol(-1) for PDEAAm (dispersity ? = 1.4-1.8) and from 1200 to 2600 g mol (-1) for PNIPAM (? = 1.7-2.1). The LCST behavior of the cellulose-graft-copolymers was studied via the determination of cloud point temperatures, evidencing that the thermoresponsive properties of the hybrid materials could be finely tuned between 18 and 26 °C for PDEAAm and between 22 and 26 °C for PNIPAM side chains. PMID:24833429

Hufendiek, Andrea; Trouillet, Vanessa; Meier, Michael A R; Barner-Kowollik, Christopher

2014-07-14

59

Polystyrene grafting from silica nanoparticles via Nitroxide-Mediated-Polymerization (NMP): synthesis and SANS analysis with contrast  

E-print Network

Polystyrene grafting from silica nanoparticles via Nitroxide-Mediated- Polymerization (NMP and efficient "grafting from" method to obtain well defined polystyrene (PS) silica nanoparticles. The method, the dimethylacetamide, which is also a good solvent for the polystyrene. The synthesis parameters have been optimized

Paris-Sud XI, Université de

60

Amphiphilic polysaccharide-hydrophobicized graft polymeric micelles for drug delivery nanosystems.  

PubMed

Self-assembled amphiphilic graft copolymers in aqueous solution to form polymeric micelles, have received growing scientific attention over the years. Among the polymeric micelles, hydrophobicized polysaccharides have currently become one of the hottest researches in the field of drug delivery nanosystems. It is attributable to such appealing properties as small particle size and narrow size distribution, distinctive core-shell structure, high solubilization capacity and structural stability, tumor passive localization by enhanced permeability and retention (EPR) effect, active targeting ability via tailored targeting promoiety, long-circulation property and facile preparation. The polymeric micelles self-assembled by hydrophobicized polysaccharides can be employed as targeted drug delivery nanosystem by including thermo- or pH-sensitive components or by attaching specific targeted moieties to the outer hydrophilic surface. Beside encapsulation of water-insoluble drugs, hydrophobicized polysaccharide polymeric micelles can complex with charged proteins or peptide drugs through electrostatic force or hydrogen bond, and serve as an effective non-viral vector for gene delivery. In the latter case, polymeric micelles can not only markedly protect these macromolecules from degradation by protease or ribozymes, but also increase the gene transfection efficiency. This review will highlight the state of the art self-assembled mechanism, characterization, preparation methods and surface modification of hydrophobicized polysaccharide polymeric micelles and their recent rapid applications as drug delivery nanosystems. PMID:21568897

Liu, Y; Sun, J; Zhang, P; He, Z

2011-01-01

61

Gamma radiation-induced grafting of glycidyl methacrylate (GMA) onto water hyacinth fibers  

NASA Astrophysics Data System (ADS)

Water hyacinth fibers (Eichhornia crassipes) were functionalized using radiation-induced graft polymerization of glycidyl methacrylate by ?-rays from 60Co source. The simultaneous grafting technique was employed wherein the water hyacinth fibers were irradiated in nitrogen atmosphere in the presence of glycidyl methacrylate dissolved in water/methanol solvent. The effects of different grafting parameters to the grafting yield were evaluated. The optimal values of solvent, absorbed dose, dose rate, and concentration of monomer were found to be 1:3 (volume/volume) water-methanol solvent, 10 kGy, 8 kGy h-1 dose rate and 5% volume/volume glycidyl methacrylate, respectively. Using the optimum conditions, degree of grafting of approximately 58% was achieved. The grafted water hyacinth fibers were characterized using Attenuated Total Reflectance-Fourier Transformed Infrared Spectroscopy (ATR-FTIR), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). The results of these tests confirmed the successful grafting of glycidyl methacrylate onto water hyacinth fibers.

Madrid, Jordan F.; Nuesca, Guillermo M.; Abad, Lucille V.

2013-04-01

62

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates  

PubMed Central

This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49?nm thick on Si, and between 13 and 35?nm thick on Ti. AFM determined root-mean-square roughness values were ?2?nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone. PMID:24482558

Foster, Rami N.; Keefe, Andrew J.; Jiang, Shaoyi; Castner, David G.

2013-01-01

63

Polyglycerol dendrimers immobilized on radiation grafted poly-HEMA hydrogels: Surface chemistry characterization and cell adhesion  

NASA Astrophysics Data System (ADS)

Radiation induced grafting of poly(2-hydroxyethylmethacrylate) (PHEMA) on low density polyethylene (LDPE) films and subsequent immobilization of poly(glycerol) dendrimer (PGLD) has been performed with the aim to improve cell adhesion and proliferation on the surface of the polymer, in order to enhance their properties for bone tissue engineering scaffolding applications. Radiation grafting of PHEMA onto LDPE was promoted by ?-ray radiation. The covalent immobilization of PGLD on LDPE-g-PHEMA surface was performed by using a dicyclohexyl carbodiimide (DCC)/N,N-dimethylaminopyridine (DMAP) method. The occurrence of grafting polymerization of PHEMA and further immobilization of PGLD was quantitatively confirmed by photoelectron spectroscopy (XPS) and fluorescence, respectively. The LDPE-g-PHEMA surface topography after PGLD coupling was studied by atomic force microscopy (AFM). The hydrophilicity of the LDPE-g-PHEMA film was remarkably improved compared to that of the ungrafted LDPE. The core level XPS ESCA spectrum of PHEMA-grafted LDPE showed two strong peaks at 286.6 eV (from hydroxyl groups and ester groups) and 289.1 eV (from ester groups) due to PHEMA brushes grafted onto LDPE surfaces. The results from the cell adhesion studies show that MCT3-E1 cells tended to spread more slowly on the LDPE-g-PHEMA than on the LDPE-g-PHEMA-i-PGLD.

Higa, Olga Z.; Faria, Henrique Antonio Mendonça; de Queiroz, Alvaro A. A.

2014-05-01

64

Radiation-induced grafting of acrylic acid onto polyethylene filaments  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of acrylic acid onto high density polyethylene (PE) filaments was carried out in order to raise softening temperature and impart flame retardance and hydrophilic properties. Mutual ?-irradiation method was employed for the grafting in a mixture of acrylic acid (AA), ethylene dichloride and water containing a small amount of ferrous ammonium sulfate. The rate of grafting was very low at room temperature. On the other hand, large percent grafts were obtained when the grafting was performed at an elevated temperature. Activation energy for the initial rate of grafting was found to be 17 {kcal}/{mol} between 20 and 60°C and 10 {kcal}/{mol} between 60 and 80°C. Original PE filament begins to shrink at 70°C, show maximum shrinkage of 50% at 130°C and then breaks off at 136°C. When a 34% AA graft is converted to metallic salt such as sodium and calcium, the graft filament retains its filament form even above 300°C and gives maximum shrinkage of 15%. Burning tests by a wire-netting basket method indicate that graft filaments and its metallic salts do not form melting drops upon burning and are self-extinguishing. Original PE filament shows no moisture absorption, however, that of AA-grafted PE increases with increasing graft percent. The sodium salt of 15% graft shows the same level of moisture regain as cotton. The AA-grafted PE filament and its metallic salts can be dyed with cationic dyes even at 1% graft. Tensile properties of PE filament is impaired neither by grafting nor by conversion to metallic salts.

Kaji, K.; Okada, T.; Sakurada, I.

65

Preparation of acrylate IPN copolymer latexes by radiation emulsion polymerization  

NASA Astrophysics Data System (ADS)

Radiation-induced and chemical initiation are compared in the initiation of acrylate emulsion copolymer latexes. The particle diameter, distribution and microstructure are influenced by emulsifier concentration, radiation dose and temperature. The results show that the emulsion particle diameter of radiation polymerization is smaller and better distributed in comparison to using chemical polymerization. In addition, interlude polymer net (IPN) core-shell copolymer latexes are observed by transmission electron microscope (TEM). The bounding face of core-shell acrylate copolymmer texes of radiation polymerization is clearer. The morphology of acrylate IPN copolymer latexes is further investigated.

Wu, Minghong; Zhou, Ruimin; Ma, Zue-Teh; Bao, Borong; Lei, Jianqiu

1997-03-01

66

Enhanced photorefractivity in a polymeric composite photosensitized with carbon nanotubes grafted to a photoconductive polymer  

NASA Astrophysics Data System (ADS)

We report on the photosensitization of photorefractive (PR) polymeric composites through the inclusion of multiwalled and singlewalled carbon nanotubes (CNTs), respectively, having poly(N-vinyl carbazole) (PVK) grafted to their surfaces. The PR nature of the holographic gratings was confirmed via the asymmetric exchange of energy in a two-beam-coupling (TBC) geometry, yielding TBC gain coefficients approaching 80 cm-1. In addition, in degenerate-four-wave-mixing experiments the prepared composites exhibited diffraction efficiencies as high as 60% and overmodulation voltages as low as ˜40 V/?m. These notable figures of merit indicate that the grafting of the PVK polymer to the various CNTs results in enhanced PR performance. The mechanism responsible for this enhancement in PR performance is investigated using a variety of experimental techniques.

Lingam, Naveen K.; Kalghatgi, Sonali; Winiarz, Jeffrey G.

2011-01-01

67

Modification of polyetherurethane for biomedical application by radiation-induced grafting. I. Grafting procedure, determination of mechanical properties, and chemical modification of grafted films  

Microsoft Academic Search

Radiation grafting of monomers onto suitable trunk polymers is a useful tool for tailoring new polymers for special purposes. This technique has been used in the past for the development of biocompatible materials, e.g., by grafting hydrogels onto mechanically stable polymers. In this first part of our work, the radiation grafting of hydrophilic or reactive monomers onto a polyetherurethane film

B. Jansen; G. Ellinghorst

1985-01-01

68

Surface modification and functionalization of electroactive polymer films via grafting of polyelectrolyte, polyampholyte and polymeric acids  

Microsoft Academic Search

Films of electroactive polymers, such as polyaniline (PAN) in its emeraldine base form, and poly(3-alkylthiophene), poly(3-hexylthiophene) (P6TH), poly(3-octylthiophene) (P8TH), and poly(3-dodecylthiophene) (P12TH) can be readily functionalized via thermal or near ultraviolet-light-induced surface graft copolymerization with monomers of polyelectrolyte, polyampholyte and polymeric acids. The monomers used in the present work include dimethyl sulphate quaternized dimethylamino-ethylmethacrylate (DMAEM·C2H6SO4), 3-dimethyl(methacryloyloxyethyl)ammonium propane sulphonate (DMAPS), acrylic

E. T. Kang; K. L. Tan; D. J. Liaw; H. H. Chiang

1996-01-01

69

DFT study of the ring opening polymerization of ?-caprolactone by grafted lanthanide complexes: 2--Effect of the initiator ligand.  

PubMed

The influence of the initiator ligand on the Ring Opening Polymerization (ROP) of ?-caprolactone by lanthanide complexes grafted on silica have been investigated by means of density functional theory (DFT) calculations. Three different initiator ligands (alkyl, dialkylamido and borohydride) and three grating modes (mono-grafted, bi-grafted or bi-grafted after breaking of a Si-O-Si bridge) have been considered. This study highlights that lanthanum grafted complexes (alkyl, amide or borohydride) are active in lactone polymerization. In any case the reaction process is demonstrated to be similar to the one found for homogeneous catalysts. However, even if the different grafting modes are energetically equivalent for the ?-caprolactone ROP initiation reaction, some differences are observed according to the ligand involved in the initiation reaction. In agreement with experimental data, grafted lanthanide amides rapidly polymerise the ?-caprolactone. The grafted alkyl lanthanum complexes are also predicted to be very efficient catalysts. The borohydride is thus predicted to be the least efficient due to the difficulties in the ring opening. Indeed, the rate-determining step is the nucleophilic attack for the methyl and dialkylamido ligands (occuring with a low barrier) whereas it is the ring opening for the borohydride ligands (highest barrier) and the formation of -CH(2)C(=O)(X) (X = CH(3) or NMe(2)) terminal group is more favorable than that of a -CH(2)OBH(2) end group. PMID:21918766

Del Rosal, Iker; Poteau, Romuald; Maron, Laurent

2011-11-14

70

PEG Molecular Net-Cloth Grafted on Polymeric Substrates and Its Bio-Merits  

PubMed Central

Polymer brushes and hydrogels are sensitive to the environment, which can cause uncontrolled variations on their performance. Herein, for the first time, we report a non-swelling “PEG molecular net-cloth” on a solid surface, fabricated using a novel “visible light induced surface controlled graft cross-linking polymerization” (VSCGCP) technique. Via this method, we show that 1) the 3D-network structure of the net-cloth can be precisely modulated and its thickness controlled; 2) the PEG net-cloth has excellent resistance to non-specific protein adsorption and cell adhesion; 3) the mild polymerization conditions (i.e. visible light and room temperature) provided an ideal tool for in situ encapsulation of delicate biomolecules such as enzymes; 4) the successive grafting of reactive three-dimensional patterns on the PEG net-cloth enables the creation of protein microarrays with high signal to noise ratio. Importantly, this strategy is applicable to any C-H containing surface, and can be easily tailored for a broad range of applications. PMID:24845078

Zhao, Changwen; Lin, Zhifeng; Yin, Huabing; Ma, Yuhong; Xu, Fujian; Yang, Wantai

2014-01-01

71

Preparation of polymer decorated graphene oxide by ?-ray induced graft polymerization.  

PubMed

Herein, we report a facile approach to decorate graphene oxide (GO) sheets with poly(vinyl acetate) (PVAc) by ?-ray irradiation-induced graft polymerization. The content of PVAc in the obtained sample, i.e., PVAc grafted GO (GO-g-PVAc) is calculated by the loss weight in thermogravimetric analysis (TGA) curves. A GO-g-PVAc sample with a degree of grafting (DG) of 28.5% was well dispersed in common organic solvents and the dispersions obtained were extremely stable at room temperature without any aggregation, even after standing for 2 months. The excellent dispersibility and stability of GO-g-PVAc in common organic solvents are readily rationalized in terms of the full coverage of PVAc chains and solvated layer formation on graphene oxide sheets surface, which weakens the interlaminar attraction of GO sheets. This approach presents a facile route for the preparation of dispersible GO and shows great potential in the preparation of graphene-based composites by solution-processes. PMID:22307684

Zhang, Bowu; Zhang, Yujie; Peng, Cheng; Yu, Ming; Li, Linfan; Deng, Bo; Hu, Pengfei; Fan, Chunhai; Li, Jingye; Huang, Qing

2012-03-01

72

Synthesis of polymer-polymer nanocomposites using radiation grafting techniques  

NASA Astrophysics Data System (ADS)

Fabrication of polymer-polymer nanocomposites based on sub-micron electrospun fibers imbedded in a distinct matrix is dependent on being able to control the wetting behavior of the electrospun fibrous mats. In this work the use of radiation grafting to modify electrospun polysulfone fiber surfaces with acrylamide is presented. Pre-irradiation grafting using electron beam (EB) and plasma treatments have been evaluated. The grafted fibrous mats were characterized using contact angle measurements, XPS, ATR-FTIR, and ESEM. It was found that 3 MeV EB can be used to obtain controlled degrees of grafting by varying total dose and that such grafting is uniform throughout the thickness of the fiber mat. In contrast, plasma grafting resulted in a concentration gradient of grafted acrylamide through the thickness with highest grafting yield on the surface of the mat exposed directly to the plasma. Procedures based on these techniques can be employed to generate polymer-polymer nanocomposites of dissimilar materials with geometric characteristics derived from the templating material.

Robinette, E. J.; Palmese, G. R.

2005-07-01

73

Radiation grafting of NIPAAm on PVDF nuclear track membranes  

NASA Astrophysics Data System (ADS)

Polymer surface modifications are obtained by the application of radiation treatments and other physico-chemical methods: fragment fission (ff) or ion implantation, etching and grafting procedure. Poly vinylidene fluoride (PVDF) foils were irradiated during different times to produce pores of different diameters through the foils. In this way, nuclear track membranes (NTM) were produced with different track diameters and track numbers. Active sites were formed using a ?-ray Co-60 source and then contacted with N-isopropylacrylamide (NIPAAm) to obtain a graft copolymer that responds to environmental conditions. The present work shows the grafting yield as a function of: ?-dose, NIPAAm concentration, pore diameter, track density, etc.

Mazzei, Ruben; Smolko, Eduardo; Tadey, Daniel; Gizzi, Laura

2000-10-01

74

Radiation-induced grafting of glycidyl methacrylate onto cotton fabric waste and its modification for anchoring hazardous wastes from their solutions.  

PubMed

Ion exchange adsorbents based on cellulosic fabric wastes carrying sulfonic acid and amine functional groups were synthesized by radiation-induced graft polymerization of glycidyl methacrylate (GMA) with subsequent chemical modification of the epoxy groups of poly-GMA graft chains with sodium sulfite/H(2)SO(4) and triethylamine, respectively. The conversion of epoxy groups into the functional groups was investigated. Factors affecting on grafting process such as radiation dose, monomer concentration and solvent were studied. The synthesized adsorbent and its applications in the removal of different types of hazardous pollutants e.g. acidic dye, cobalt, dichromate and phenols from aqueous solution were also studied. PMID:19297095

Sokker, Hesham H; Badawy, Sayed M; Zayed, Ehab M; Nour Eldien, Faten A; Farag, Ahmad M

2009-08-30

75

Additive effects common to radiation grafting and wood plastic composite formation  

NASA Astrophysics Data System (ADS)

A range of additives has been developed for enhancing grafting yields in a variety of systems initiated by ionizing radiation. Cellulose has been adopted as the predominant naturally occurring model backbone polymer in these studies because of its structural relationship to wood which is the reference substrate for the work reported in the related second part of this paper concerning composites. Some experiments have been performed with the other major naturally occurring polymer, wool. For comparison purposes with synthetic materials, some studies have also been performed with polypropylene as trunk polymer. Styrene has been used as a predominant monomer in grafting with some experiments utilizing the acrylates like methyl methacrylate. The role of solvent in grafting has been evaluated. UV has been used as initiator to replace ionizing radiation for certain experiments. The additives used were mineral acids, lithium salts, multifunctional acrylates and their methacrylate analogues, urea, oligomer acrylates, silane, fluorinated alkyl esters and thermal free radical initiators. A mechanism to explain the additive effect in terms of reagent partitioning has been proposed. The most efficient of the additives in grafting have been applied to the radiation synthesis of wood-polymer composites using two different types of wood, namely simul from Bangladesh and Pinus radiata from Australia with two different monomers with and without solvent, namely butyl methacrylate and methyl methacrylate. The effect of the additives on the physical properties, such as polymer loading and tensile strength, of the wood composites were determined. The partition concept developed for grafting has been used to explain the reactivity of the additives in wood plastic formation. The polymerization of monomers in wood plastic systems is shown to be related to simple homopolymerization of monomers in solution, a reaction which is also shown to be capable of interpretation in terms of partition phenomena.

Garnett, John L.; Ng, Loo-Teck

1996-08-01

76

Synthesis of pH-responsive polysilane with polyelectrolyte side chains through ?-ray-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Polysilanes with polyelectrolyte side chains are synthesized by two methods utilizing ?-ray-induced grafting and the pH responsiveness for one of those polymers is revealed mainly by investigating interfacial behavior of its monolayer at the air/water interface. In the first synthetic method, poly(methyl acrylate) is grafted onto poly(methyl- n-propylsilane) (PMPrS) through ?-ray-induced grafting, and then the PMA chains are hydrolyzed to poly(acrylic acid) resulting in the yield of ca. 97%. Thus PMPrS with polyelectrolyte side chains is successfully synthesized by the graft chain hydrolysis. The other method is the direct grafting of electrolyte monomers. Poly(methacrylic acid)-grafted PMPrS (PMPrS- g-PMAA) can be obtained through ?-ray-induced grafting of methacrylic acid monomers onto PMPrS chains, which shows the effectiveness of radiation grafting for the synthesis of polyelectrolyte graft copolymers. PMPrS- g-PMAA exhibits pH responsive behavior. In addition to the pH-dependence of water solubility, interfacial behavior also depends on the pH. Langmuir monolayers of PMPrS- g-PMAA exhibit different surface pressure-area isotherms according to the grafting yield and the pH of the subphase water. This result suggests that radiation modification is useful for fabricating polysilane-based ordered materials responsive to outer stimuli.

Tanaka, Hidenori; Kawade, Yasushi; Sato, Nobuhiro; Matsuyama, Tomochika

2012-02-01

77

Evaluation of microwave assisted grafted sago starch as controlled release polymeric carrier.  

PubMed

In the present investigation an attempt has been made to develop a new co-polymeric material for controlled release tablet formulations. The acrylamide grafting was successfully performed on the backbone of sago starch. The modified starch was tested for acute toxicity and drug-excipient compatibility study. The grafted material was used in making of controlled release tablets of lamivudine. The formulations were evaluated for physical characteristics such as hardness, friability, %drug content and weight variations. The in vitro release study showed that the optimized formulation exhibited highest correlation (R) value in case of Higuchi model and the release mechanism of the optimized formulation predominantly exhibited combination of diffusion and erosion process. There was a significant difference in the pharmacokinetic parameters (T(max), C(max), AUC, V(d), T(1/2) and MDT) of the optimized formulation as compared to the marketed conventional tablet Lamivir(®) was observed. The pharmacokinetics parameters were showed controlled pattern and better bioavailability. The optimized formulation exhibited good stability and release profile at the accelerated stability conditions. PMID:23707750

Singh, Akhilesh Vikram; Nath, Lila Kanta

2013-09-01

78

Controlling the cell adhesion property of silk films by graft polymerization.  

PubMed

We report here a graft polymerization method to improve the cell adhesion property of Bombyx mori silk fibroin films. B. mori silk has evolved as a promising material for tissue engineering because of its biocompatibility and biodegradability. However, silk's hydrophobic character makes cell adhesion and proliferation difficult. Also, the lack of sufficient reactive amino acid residues makes biofunctionalization via chemical modification challenging. Our study describes a simple method that provides increased chemical handles for tuning of the surface chemistry of regenerated silk films (SFs), thus allowing manipulation of their bioactivity. By grafting pAAc and pHEMA via plasma etching, we have increased carboxylic acid and hydroxyl groups on silk, respectively. These modifications allowed us to tune the hydrophilicity of SFs and provide functional groups for bioconjugation. Our strategy also allowed us to develop silk-based surface coatings, where spatial control over cell adhesion can be achieved. This control over cell adhesion in a particular region of the SFs is difficult to obtain via existing methods of modifying the silk fibroin instead of the SF surface. Thus, our strategy will be a valuable addition to the toolkit of biofunctionalization for enhancing SFs' tissue engineering applications. PMID:24650047

Dhyani, Vartika; Singh, Neetu

2014-04-01

79

Radiation induced grafting of acrylic acid onto extruded polystyrene surface  

NASA Astrophysics Data System (ADS)

Polystyrene materials with good solubility in liquid scintillation cocktails are used to wipe off different types of surfaces in order to determine the tritium removable contamination with the help of a liquid scintillation counter. This paper analyses hydrophilic surface modifications by radiation induced grafting of acrylic groups onto extruded polystyrene plates. Two grafting methods were used: (a) exposure of extruded polystyrene plates, immersed in aqueous acrylic acid solution, to a gamma radiation of a Co-60 source, and (b) exposure of extruded polystyrene plates to a Co-60 source, followed by the immersion of extruded polystyrene plates in aqueous acrylic acid solution. The grafting of acrylic was proved by IR spectrometry and by radiometric methods using acrylic acid labelled with tritium.

Fugaru, Viorel; Bubueanu, George; Tuta, Catalin

2012-09-01

80

EUV lithographic radiation grafting of thermo-responsive hydrogel nanostructures  

NASA Astrophysics Data System (ADS)

Nanostructures of the thermoresponsive poly( N-isopropyl acrylamide) (PNIPAAm) and of PNIPAAm-block-poly(acrylic acid) copolymers were produced on poly(tetrafluoroethylene-co-ethyelene) (ETFE) films using extreme ultraviolet (EUV) lithographic exposure with subsequent graft-polymerization. The phase transition of PNIPAAm nanostructures at the low critical solution temperature (LCST) at 32 °C was imaged by atomic force microscopy (AFM) phase contrast measurements in pure water. Results show a higher phase contrast for samples measured below the LCST temperature than for samples above the LCST, proving that the soft PNIPAAm hydrogel transforms into a much more compact conformation above the LCST. EUV lithographic exposures were combined with the reversible addition-fragment chain transfer (RAFT)-mediated polymerization using cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agent to synthesize PNIPAAm block-copolymer nanostructures.

Farquet, Patrick; Padeste, Celestino; Solak, Harun H.; Gürsel, Selmiye Alkan; Scherer, Günther G.; Wokaun, Alexander

2007-12-01

81

Radiation grafting of NIPAAm on PVDF nuclear track membranes  

Microsoft Academic Search

Polymer surface modifications are obtained by the application of radiation treatments and other physico-chemical methods: fragment fission (ff) or ion implantation, etching and grafting procedure. Poly vinylidene fluoride (PVDF) foils were irradiated during different times to produce pores of different diameters through the foils. In this way, nuclear track membranes (NTM) were produced with different track diameters and track numbers.

Ruben Mazzei; Eduardo Smolko; Daniel Tadey; Laura Gizzi

2000-01-01

82

Flash polymerization of silicone oils using gamma radiation for conserving waterlogged wood  

E-print Network

radiation doses induced polymerization in the oil to such an extent the cells swelled and became extremely distorted. However, for the same fully bulked samples, small radiation doses produced little to moderate polymerization of the oil in the wood cells...

Gidden, Richmond Paul

2012-06-07

83

Controlled grafting from poly(vinylidene fluoride) microfiltration membranes via reverse atom transfer radical polymerization and antifouling properties  

Microsoft Academic Search

A reverse atom transfer radical polymerization (RATRP) with benzoyl peroxide (BPO)\\/CuCl\\/2,2-bipyridine (Bpy) was applied onto grafting of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) microfiltration (MF) membrane surfaces, including the pore surfaces. The introduction of peroxide and hydroperoxide groups onto the PVDF membranes was achieved by ultraviolet (UV) irradiation in nitrogen, followed by

Yiwang Chen; Qilan Deng; Jichun Xiao; Huarong Nie; Lichuan Wu; Weihua Zhou; Biwu Huang

2007-01-01

84

Comparison of pre-irradiation and mutual grafting of 2-chloroacrylonitrile on cellulose by gamma-irradiation  

NASA Astrophysics Data System (ADS)

Radiation-induced graft polymerization is one of the best methods for obtaining materials with new properties. In this work, radiation grafting of 2-chloroacrylonitrile to cellulose by mutual and pre-irradiation grafting methods was investigated. The grafting yield was enhanced by applying the emulsion grafting method. The grafting yield determined in the above systems was observed as 27% at highest and 6% at lowest. The effects of concentration of monomer, reaction time and reaction temperature on grafting yield were studied. Evidence of grafting has been based on the comparative studies of cellulose and grafted cellulose by infrared spectroscopy, thermal analysis and contact angle measurement. Grafting enhances thermal stability of cellulose backbone.

?olpan, Dilek; Torun, Murat; Güven, Olgun

2010-03-01

85

EMULSION POLYMERIZATION OF VINYL MONOMERS UNDER THE INFLUENCE OF IONIZING RADIATION  

Microsoft Academic Search

The kinetics of emulsion polymerization induced by BETA , gamma , and ; x radiation are discussed. Such ionizing radiations induce the polymerization of ; some vinyl monomers in aqueous emulsion with high radiation yields, and with ; identical emulsion compositions, the kinetics of this reaction and the kinetics ; of emulsion polymerization induced by water-soluble initiators are very similar.

D. Hummel

1963-01-01

86

In vivo evaluation of novel chitosan graft polymeric micelles for delivery of paclitaxel.  

PubMed

A water-insoluble anti-tumor agent, Paclitaxel (PTX) was successfully incorporated into polymeric micelles formed from new graft copolymers, N-octyl-N-(2-carboxyl-cyclohexamethenyl) chitosan derivatives(OCCC). The objective of this study was to optimize and characterize the novel PTX micelle (PTX-M). Furthermore, the pharmacokinetics, NIR-imaging, biodistribution, and anti-tumor effects of PTX-M were evaluated. The results showed that the PTX-M had high drug loading (43.25%). The Vd and t1/2? of PTX-M were increased by 11.4- and 2.83-fold, respectively, but the plasma AUC of PTX-M was 3.8-fold lower than that of Taxol. Biodistribution study indicated that PTX-M was widely distributed into most tissues, most of them found in liver, spleen, lung, and kidney. This result was similar with NIR(near-infrared)-imaging. Tumor growth was significantly inhibited after intravenous injection of PTX-M. PTX-M showed the enhanced anti-tumor effect and non-toxic effects compared with Taxol, the commercial product of PTX. Therefore, the chitosan-derived micelle system offered a stable and effective platform for cancer chemotherapy with PTX. PMID:20942638

Liu, Jia; Li, Hongxia; Chen, Daquan; Jin, Xiang; Zhao, Xiaoliang; Zhang, Can; Ping, Qineng

2011-04-01

87

Modification on liquid retention property of cassava starch by radiation grafting with acrylonitrile. I. Effect of ?-irradiation on grafting parameters  

NASA Astrophysics Data System (ADS)

Radiation modification on liquid retention properties of native cassava starch, gelatinized at 85°C, by graft copolymerization with acrylonitrile was carried out by mutual irradiation to gamma-rays. A thin aluminum foil was used to cover the inner wall of the reaction vessel, so that the homopolymer concentration was reduced to be less than 1.0% with a distilled water retention value of 665 g/g of the dry weight of the saponified grafted product. Confirmation of graft copolymerization and saponification reactions was made by the infrared spectrophotometric technique. The combined effect of radiation parameters in terms of an irradiation time and a dose rate to the total dose on the extent of the grafting reaction expressed in terms of grafting parameters which directly influenced liquid retention values was evaluated in conjunction with statistical analysis.

Kiatkamjornwong, S.; Chvajarernpun, J.; Nakason, C.

1993-07-01

88

Polystyrene grafting from silica nanoparticles via Nitroxide-Mediated-Polymerization (NMP): synthesis and SANS analysis with contrast variation method  

E-print Network

We present a new convenient and efficient "grafting from" method to obtain well defined polystyrene (PS) silica nanoparticles. The method, based on Nitroxide-Mediated Polymerization (NMP), consists to bind covalently the alkoxyamine, which acts as initiator controller agent, at the silica nanoparticles surface in two steps. The first step is a reaction between the aminopropylsilane and the silica particles in order to functionalize the particles surface with amino group. In a second step, the initiating-controlling alkoxyamine moiety is introduced via an over grafting reaction between the amino group and the N-hydroxysuccinimide based MAMA-SG1 activated ester. To simplify both their chemical transformation and the polymerization step, the native silica particles, initially dispersed in water, have been transferred in an organic solvent, the dimethylacetamide, which is also a good solvent for the polystyrene. The synthesis parameters have been optimized for grafting density, conversion rates, and synthesis reproducibility while keeping the colloidal stability and to avoid any aggregation of silica particles induced by the inter-particles interaction evolution during the synthesis. After synthesis, the final grafted objects have been purified and the non-grafted polymer chains formed in the solvent have been washed out by ultra filtration. Then the particles have been studied using Small angle Neutron Scattering (SANS) coupled to neutron contrast variation method. To optimize the contrast conditions, both hydrogenated and deuterated monomers have been used for the synthesis. A refined fitting analysis based on the comparison on two models, a basic core-shell and the Gaussian Pedersen model, enables us to fit nicely the experimental data for both the hydrogenated and deuterated grafted case. Differences are seen between grafting of normal or deuterated chains which can be due to monomer reactivity or to neutron contrast effect variations. The synthesis and the characterization method established in this work constitute a robust and reproducible way to design well defined grafted polymer nanoparticles. These objects will be incorporated in polymer matrices in a further step to create Nanocomposites for polymer reinforcement.

Chloé Chevigny; Didier Gigmes; Denis Bertin; Jacques Jestin; François Boué

2010-05-10

89

Graft polymerization of acrylic acid and methacrylic acid onto poly(vinylidene fluoride) powder in presence of metallic salt and sulfuric acid  

NASA Astrophysics Data System (ADS)

Poly(vinylidene fluoride) (PVDF) powder was grafted with acrylic acid (AAc) or methacrylic acid (MAA) by the pre-irradiation induced graft polymerization technique. The presence of graft chains was proven by FT-IR spectroscopy. The degree of grafting (DG) was calculated by the acid-base back titration method. The synergistic effect of acid and Mohr's salt on the grafting kinetics was examined. The results indicated that adding sulfuric acid and Mohr's salt simultaneously in AAc or MAA solutions led to a strong enhancement in the degree of grafting. The grafted PVDF powder was cast into microfiltration (MF) membranes using the phase inversion method and some properties of the obtained MF membranes were characterized.

Deng, Bo; Yu, Yang; Zhang, Bowu; Yang, Xuanxuan; Li, Linfan; Yu, Ming; Li, Jingye

2011-02-01

90

Development of hydrogels by radiation induced polymerization for use in slow drug delivery  

NASA Astrophysics Data System (ADS)

In the present work, in order to improve the drug release profile of indinavir sulfate, a potent inhibitor of HIV protease, controlled drug delivery systems in the form of hydrogels have been designed by a radiation graft polymerization method. These hydrogels have been prepared by using dietary fiber psyllium and binary monomers mixture of acrylamide (AAm) and 2-acrylamido-2-methylpropanesulfonic acid (AMPSA). These polymers have been characterized with cryo-SEMs, FTIR, XRD and swelling studies. The swelling of hydrogels has been determined in solution of different pH, temperature and [NaCl]. in vitro release studies of model drug indinavir sulfate in different pH have been carried out to determine the drug release mechanism. The release of dug occurred through non-Fickian mechanism.

Singh, Baljit; Bala, R.

2014-10-01

91

A substrate-independent method for surface grafting polymer layers by atom transfer radical polymerization: reduction of protein adsorption.  

PubMed

A general method for producing low-fouling biomaterials on any surface by surface-initiated grafting of polymer brushes is presented. Our procedure uses radiofrequency glow discharge thin film deposition followed by macro-initiator coupling and then surface-initiated atom transfer radical polymerization (SI-ATRP) to prepare neutral polymer brushes on planar substrates. Coatings were produced on substrates with variable interfacial composition and mechanical properties such as hard inorganic/metal substrates (silicon and gold) or flexible (perfluorinated poly(ethylene-co-propylene) film) and rigid (microtitre plates) polymeric materials. First, surfaces were functionalized via deposition of an allylamine plasma polymer thin film followed by covalent coupling of a macro-initiator composed partly of ATRP initiator groups. Successful grafting of a hydrophilic polymer layer was achieved by SI-ATRP of N,N'-dimethylacrylamide in aqueous media at room temperature. We exemplified how this method could be used to create surface coatings with significantly reduced protein adsorption on different material substrates. Protein binding experiments using labelled human serum albumin on grafted materials resulted in quantitative evidence for low-fouling compared to control surfaces. PMID:22023749

Coad, Bryan R; Lu, Yi; Meagher, Laurence

2012-02-01

92

Radiation-induced grafting of cellulose for adsorption of hazardous water pollutants: A review  

NASA Astrophysics Data System (ADS)

This review paper briefly introduces the radiation chemistry of cellulose, the different grafting techniques used, and the methods of characterization of the grafted material. It shows the application of the grafted polymer for the removal of water pollutants and also the regeneration of the adsorbent.

Wojnárovits, L.; Földváry, Cs. M.; Takács, E.

2010-08-01

93

Heterogenization of precious metal catalysts and enzymes by radiation-induced graft copolymerization. [Gamma or ultraviolet radiation  

Microsoft Academic Search

The feasibility of using radiation graft copolymerization for the preparation of supports suitable for the heterogenization of catalysts was examined. To bind metal complexes, radiation graft copolymers of p-styryldiphenylphosphine with a number of trunk polymers were produced. Similarly enzyme immobilization was successful on chemically modified p-nitrostyrene copolymers. Conditions for ..gamma.. and\\/or UV radiation grafting of styrene, p-styryldiphenylphosphine, vinyldiphenylphosphine and p-nitrostyrene

Levot

1983-01-01

94

Grafting of polyethylene by ?-radiation grafting onto conductive carbon black and application as novel gas and solute sensors  

NASA Astrophysics Data System (ADS)

?-Ray radiation grafting of polyethylene (PE) onto conductive carbon black under various conditions was investigated. In the case of 400 kGy dose of irradiation of PE-adsorbed carbon black at high temperatures near or above the melting point of PE, the grafting of PE onto the carbon black surface was successfully proceeded and the percentage of grafting exceeded 90%. Using the PE-grafted carbon black and PE, conductive composite prepared from PE-grafted carbon black and PE was prepared. The electric resistance of the composite largely increased when it was transferred from dry air to solvent vapor, such as carbon tetrachloride and cyclohexane. The electric resistance also clearly increased when the composite was immersed in n-hexane solution of tetrahydrofuran, chloroform and cyclohexane. Therefore, it was concluded that the conductive composite could be used as a novel sensor of solvent vapor and solute in n-hexane.

Chen, J.; Iwata, H.; Maekawa, Y.; Yoshida, M.; Tsubokawa, N.

2003-06-01

95

Grafting acrylic polymers from flat nickel and copper surfaces by surface-initiated atom transfer radical polymerization.  

PubMed

Acrylic polymers, including poly(methyl methacrylate), poly(2,2,2-trifluoroethyl methacrylate), poly( N,N'-dimethyaminoethyl methacrylate), and poly(2-hydroxyethyl methacrylate) were grafted from flat nickel and copper surfaces through surface-initiated atom transfer radical polymerization (ATRP). For the nickel system, there was a linear relationship between polymer layer thickness and monomer conversion or molecular weight of "free" polymers. The thickness of the polymer brush films was greater than 80 nm after 6 h of reaction time. The grafting density was estimated to be 0.40 chains/nm2. The "living" chain ends of grafted polymers were still active and initiated the growth of a second block of polymer. Block copolymer brushes with different block sequences were successfully prepared. The experimental surface chemical compositions as measured by X-ray photoelectron spectroscopy agreed very well with their theoretical values. Water contact angle measurements further confirmed the successful grafting of polymers from nickel and copper surfaces. The surface morphologies of all samples were studied by atomic force microscopy. This study provided a novel approach to prepare stable functional polymer coatings on reactive metal surfaces. PMID:18507417

Chen, Renxu; Zhu, Shiping; Maclaughlin, Shane

2008-06-01

96

Influence of Radiation-Induced Grafting Process on mechanical Properties of ETFE Based Membranes  

Microsoft Academic Search

We investigated the influence of irradiation dose, crosslinker concentration, graft level or styrene\\/DVB content on the tensile strength, elongation at break, yield strength and modulus of elasticity, of poly(ethylene-alt-tetrafluoroethylene) (ETFE) based membranes. Grafted films were prepared by radiation-induced grafting and the membranes were obtained by subsequent sulfonation of the grafted films. It was found that the elongation at break decreases

H. Ben; S. Alkan Gürsel; A. Buisson; L. Gubler; A. Wokaun; G. G. Scherer

97

Crystal structure and mechanical properties of UHMWPE-g-PMA fiber prepared by radiation grafting  

NASA Astrophysics Data System (ADS)

Methyl acrylate (MA) monomer was grafted onto ultra-high molecular weight polyethylene (UHMWPE) fibers by ?-ray pre-irradiation induced graft polymerization. The grafting of MA on UHMWPE fiber was confirmed by thermogravimetric analysis and Fourier-transform infrared spectroscopy. The degree of grafting (DG) increased with an increase in absorbed dose and reached a significantly high value (approximately 200%) at 100 kGy. Scanning electron microscopy analysis revealed that the surface of the UHMWPE-g-PMA fibers was covered by the MA grafting layer and became rough. The monoclinic crystalline and orientated intermediate phases were disordered by the grafting chains such that degree of orientation declined gradually with increasing DG. The tensile strength of UHMWPE-g-PMA fiber decreased with increasing dose but was independent of DG, whereas the fiber modulus declined with DG. UHMWPE-g-PMA fiber that possesses desirable mechanical properties could be obtained at a dose of less than 10 kGy.

Xing, Zhe; Wang, Mouhua; liu, Weihua; Hu, Jiangtao; Wu, Guozhong

2013-05-01

98

Enhancement of the grafting performance and of the water absorption of cassava starch graft copolymer by gamma radiation  

NASA Astrophysics Data System (ADS)

Enhancement of the gamma radiation grafting of acrylonitrile onto gelatinized cassava starch was investigated. Infrared spectrometry was used to follow the chemical changes in the grafting reaction and from saponification. The saponified starch- g-PAN (HSPAN) was then characterized in terms of grafting parameters to provide a guide for the optimum total dose (kGy) and the appropriate ratio of starch/acrylonitrile for a fixed dose rate of 2.5 × 10 -1 kGy/min. Other dose rates were also carried out to obtain the appropriate result of grafting copolymerization and of water absorption. A thin aluminium foil, covering the inner wall of the reaction vessel, was found to be far more effective than any other metal films in the enhancement of the grafting reaction and the water absorption as well. Nitric acid in the medium increases the grafting yield and the water absorption. Methyl ether hydroquinone inhibitor was evaluated for its ability to increase homopolymerization and decrease graft reaction. When styrene was used as a comonomer, it hampered the grafting of acrylonitrile onto starch backbone. The water absorption capacity was improved by freeze-drying the HSPAN. The treatment of the HSPAN with aluminium trichloride hexahydrate was found to enhance the degree of wicking, but to decrease the water absorbency.

Kiatkamjornwong, Suda; Meechai, Nispa

1997-06-01

99

The tolerance of skin grafts to postoperative radiation therapy in patients with soft-tissue sarcoma  

SciTech Connect

During the last ten years at the National Cancer Institute, 11 patients have received 12 courses of postoperative adjuvant radiation therapy to skin grafts used for wound closure after the resection of soft-tissue sarcomas. The intervals between grafting and the initiation of radiation ranged between 3 and 20 weeks, and 4 patients received chemotherapy at the same time as their radiation. Ten of the 12 irradiated grafts remained intact after the completion of therapy. One graft had several small persistently ulcerated areas that required no further surgical treatment, and one graft required a musculocutaneous flap for reconstruction of a persistent large ulcer. Acute radiation effects on the grafted skin sometimes developed at slightly lower doses than usually seen with normal skin, but these acute effects necessitated a break in therapy on only five occasions. Concurrent chemotherapy and a relatively short interval between grafting and the initiation of radiation seemed to contribute to more severe radiation reactions. This experience indicates that postoperative adjuvant radiation therapy can be delivered to skin grafted areas without undue fear of complications, especially if the graft is allowed to heal adequately prior to initiating therapy and if chemotherapy is not given in conjunction with radiation.

Lawrence, W.T.; Zabell, A.; McDonald, H.D. (National Cancer Institute, Bethesda, MD (USA))

1986-03-01

100

Physicochemical and electrochemical characterization of battery separator prepared by radiation induced grafting of acrylic acid onto microporous polypropylene membranes  

Microsoft Academic Search

Mutual radiation grafting technique was used to graft acrylic acid on micrometer thick micro-porous polypropy- lene membrane using high-energy gamma radiation. Grafting could not be achieved in aqueous acrylic acid solution. The presence of Mohr's salt effectively retarded the homopolymerization of acrylic acid but did not lead to grafting enhance- ment. Mohr's salt in presence of acids was found to

N. K. Goel; Y. K. Bhardwaj; R. Manoharan; Virendra Kumar; K. A. Dubey; C. V. Chaudhari; S. Sabharwal; Trombay Mumbai

2009-01-01

101

Hydrophilic modification of polyethersulfone membranes by low temperature plasma-induced graft polymerization  

Microsoft Academic Search

A complete and permanent hydrophilic modification of polyethersulfone (PES) membranes is achieved by argon plasma treatment followed by polyacrylic acid (PAA) grafting in vapor phase. Both Ar plasma treatment alone and post-PAA grafting rendered a complete hydrophilicity to the PES membranes. The hydrophilicity of the membranes treated with only the Ar plasmas is not, however, permanent. In contrast, the PES

Dattatray S Wavhal; Ellen R Fisher

2002-01-01

102

Functionalization of cotton fabrics by radiation induced grafting of quaternary salt to impart antibacterial property  

NASA Astrophysics Data System (ADS)

High energy gamma radiation has been used to covalently link polymer chains of a quaternary ammonium salt containing monomer, viz. [2-(Acryloyloxyethyl)]trimethylammonium chloride (AETC) to cotton fabric by mutual radiation grafting using 2-hydroxyethyl methacrylate (2-HEMA) monomer as the grafting facilitator. Grafting yield was found to increase with the radiation dose and monomer concentration. The grafted samples have been characterized for water uptake, surface morphology and thermal stability and for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity particularly against gram-positive bacteria.

Goel, N. K.; Kumar, Virendra; Rao, M. S.; Bhardwaj, Y. K.; Sabharwal, S.

2011-11-01

103

Radiation-grafted, chemically modified membranes part I - Synthesis of a selective aluminum material  

NASA Astrophysics Data System (ADS)

Polymeric membranes were styrene grafted by irradiation methods and the obtained material was chemically modified to become aluminum selective. For this purpose, polymeric substrates of PVC (polyvinyl chloride) and PP (polypropylene) were styrene grafted mutually by gamma and electron beam irradiation. The modification process includes three basic reaction paths: Friedel-Crafts acylation, 2-methylanisole coupling and a final oxidation to achieve aluminum selectivity. Although this specific chemical modification in derivatives of polystyrene is not new, the new challenge is to obtain a selective material where original membrane characteristics (physical shape and mechanical resistance) are minimally conserved after such an aggressive treatment.

Bazante-Yamaguishi, Renata; Moura, Eduardo; Manzoli, José E.; Geraldo, Aurea B. C.

2014-01-01

104

Investigations and characterization of radiation grafted copolymers for possible practical use in waste water treatment  

NASA Astrophysics Data System (ADS)

Selective removal and recovery of metals from industrial effluent is an environmental problem and economic concern. There are a number of heavy metals that are candidates for removal prior to having waste solutions coming in contact with the environment. Therefore, a study has been made on the preparation of hydrophilic membranes having both anionic and cationic exchangers. To achieve such properties in the required membranes, a trial has been made on the radiation graft copolymerization of binary monomers possessing anionic and cationic exchangers such as acrylic acid/2- and 4-vinyl pyridine (AAc/2-VP) (AAc/4-VP) onto available commercial polymeric substrate such as low-density polyethylene (LDPE). The preparation conditions at which the grafting process proceeds homogeneously are determined. Characterization and some selected properties of the prepared grafted membranes were studied and accordingly the possibility of its practicable use in waste water treatment from heavy and toxic metals such as Pb, Zn, Cd, Fe,… etc. was investigated. The metal uptake by such prepared membranes was determined by using atomic absorption technique. The membrane efficiency and durability was investigated. The maximum uptake for a given metal was higher for the LDPE-g-P (AAc/2VP) membranes than that for the LDPE-g-P (AAc/4VP). The chelated metal ions were easily desorbed by treating the membrane with 0.1 N HCl for 2 h at room temperature. A mixture of two or three metals in the same feed solution was used to determine the selectivity of the membrane towards different metals. The results obtained for the prepared membranes showed a great promise for their applicability in the removal of heavy metals from wastewater.

Hegazy, El-Sayed A.; El-Rehim, H. A. Abd; Shawky, H. A.

2000-01-01

105

A novel polymeric flocculant based on polyacrylamide grafted inulin: aqueous microwave assisted synthesis.  

PubMed

Polyacrylamide grafted inulin (In-g-PAM) was synthesized via aqueous microwave assisted method (using ceric ammonium nitrate in synergism with microwave in aqueous medium). The intended grafting of the PAM chains on polysaccharide backbone was confirmed through standard physicochemical characterization techniques, namely intrinsic viscosity measurement, Fourier transform infrared (FTIR) spectroscopy, elemental analysis (C, H, N and O), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studies. Flocculation efficacy of various grades of synthesized grafted product was studied in coal fines suspension, in relation to inulin (parent polysaccharide). This was done utilizing jar test and settling test procedure, towards possible application as a flocculant for coal washery effluents. PMID:24274474

Rahul, Rahul; Jha, Usha; Sen, Gautam; Mishra, Sumit

2014-01-01

106

Thermoluminescence characterization of functionalized grafted polymers and its application for radiation dosimetry at low doses  

NASA Astrophysics Data System (ADS)

Functionalized polymers were prepared by radiation-induced graft copolymerization of binary monomer system acrylic acid/acrylamide (AAc/AAm) onto low-density polyethylene (LDPE) and polypropylene (PP) films using direct radiation-grafting technique. Sulfonation was carried out for the prepared grafted copolymers using concentrated sulfuric acid (97%) at 60 degrees C for 15 min. The grafted and sulfonated grafted films found to have good properties such as thermal stability and hydrophilic properties. The sulfonated grafted films found to have a better hydrophilic character than the grafted ones due to ionic character resulted by this conversion. The thermoluminescence (TL) characteristics of a set of grafted and sulfonated films have been studied with regard to their use as off-line dosimeters in radiotherapy. The structural characterization has been performed by means of infrared spectroscopy. Their TL responses have been tested with radiotherapy beams of Co-60 photons in the dose range 0.1-7 Gy. The dosimetric characterization has yielded a very good reproducibility and is independent of the radiation energy. The TL signal is not influenced by the dose rate and exhibits a very low thermal fading. Moreover, the sensitivity of the samples compares favorably with that of the standard TLD100 dosimeters. Finally, at the same dose, the TL response for LDPE-g-P (AAm/AAc) films is higher than the PP-g-P(AAm/AAc), and the sulfonated grafted films are more sensitive to radiation than the grafted ones.

Diab, H. M.; Ghaffar, A. M.; El-Arnaouty, M. B.

2005-09-01

107

Effect of UV-irradiation intensity on graft polymerization of 2-methacryloyloxyethyl phosphorylcholine on orthopedic bearing substrate.  

PubMed

Photoinduced grafting of 2-methacryloyloxyethyl phosphorylcholine (MPC) onto cross-linked polyethylene (CLPE) was investigated for its ability to reduce the wear of orthopedic bearings. We investigated the effect of UV-irradiation intensity on the extent of poly(MPC) (PMPC) grafting, and found that it increased with increasing intensity up to 7.5 mW/cm(2), and the remained fairly constant. It was found to be extremely important to carefully control the UV intensity, as at higher values, a PMPC gel formed via homopolymerization of the MPC, resulting in the formation of cracks at the interface of the PMPC layer and the CLPE substrate. When the CLPE was exposed to UV-irradiation during the graft polymerization process, some of its physical and mechanical properties were slightly changed due to cross-linking and scission effects in the surface region; however, the results of all of the tests exceed the lower limits of the ASTM standards. Modification of the CLPE surface with the hydrophilic PMPC layer increased lubrication to levels that match articular cartilage. The highly hydrated thin PMPC films mimicked the native cartilage extracellular matrix that covers synovial joint surface, acting as an extremely efficient lubricant, and providing high-wear resistance. PMID:24124003

Kyomoto, Masayuki; Moro, Toru; Yamane, Shihori; Hashimoto, Masami; Takatori, Yoshio; Ishihara, Kazuhiko

2014-09-01

108

Electroless Plating of Copper on Polyimide Film Modified by 50 Hz Plasma Graft Polymerization with 1-Vinylimidazole  

NASA Astrophysics Data System (ADS)

This paper reports on the proof of concept work on the novel process of producing metalized polyimide (PI) film by coating a layer of copper (Cu) thin film on the surface of the PI film without using any adhesive. The method which is employed to produce a metalized PI film used in flexible printed circuit (FPC) is based on plasma graft polymerization of 1-vinlyimidazole (VIDz) on plasma pre-treated PI surface. The plasma grafted PI film (VIDz-g-PI) surfaces are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). AFM results show that the PI film surface has been successfully treated and grafted with VIDz. As post-thermal treatment is known to promote adhesion strength between the metallic film and the PI surface, the effects of post-thermal treatment environment and temperature on the adhesion property of Cu plated VIDz-g-PI (Cu/VIDz-g-PI) are evaluated. Post-thermal treatment in air shows better adhesion strength than in vacuum. The adhesion strength decreases as the post-thermal treatment temperature is increased. In the present development work, the adhesion strength obtained has met the initial market targeted 9-10 N/cm adhesion strength. Samples obtained at a pre-selected plasma power and time window are able to maintain their adhesion strength after being subjected to ageing at 100 °C for 168 h.

San Wong, Chiow; Pong Lem, Hon; Tong Goh, Boon; Wie Wong, Cin

2009-03-01

109

Novel Diblock Copolymer-Grafted Multiwalled Carbon Nanotubes via a combination of Living and Controlled/Living Surface Polymerizations  

SciTech Connect

Diels Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1-benzocylcobutene-10-phenylethylene (BCB-PE) or 4-hydroxyethylbenzocyclobutene (BCB-EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and e-caprolactone (e-CL), respectively. The OH-end groups were transformed to isopropylbromide groups by reaction with 2-bromoisobutyryl bromide, for subsequent atom transfer radical polymerization of styrene or 2-dimethylaminoethyl methacrylate to afford the final diblock copolymers. 1H NMR, differential scanning calorimetry (DSC), TGA, and transmission electron microscopy (TEM) were used for the characterization of the nanocomposite materials. TEM images showed the presence of a polymer layer around the MWNTs as well as the dissociation of MWNT bundles. Consequently, this general methodology, employing combinations of different polymerization techniques, increases the diversity of diblocks that can be grafted from MWNTs.

Priftis, Dimitrios [ORNL; Sakellariou, Georgios [ORNL; Mays, Jimmy [University of Tennessee, Knoxville (UTK); Hadjichristidis, Nikos [University of Athens, Athens, Greece

2010-01-01

110

Study on radiation-induced grafting of styrene onto chitin and chitosan  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of styrene onto chitin and chitosan powder was performed at room temperature. The effect of various conditions such as absorbed dose, solvent and oxygen on grafting was investigated. The grafting yield increased with the increase in absorbed dose. At the same dose, the grafting yield of styrene on chitosan was higher than that on chitin. The grafting reaction was promoted in the presence of methanol, and oxygen delayed the grafting reaction but did not inhibit it completely. In order to study the mechanism of grafting reaction and analyze the grafted samples, the grafted products were extracted first by benzene, then they were hydrolyzed in the presence of acid and separated by thin layer chromatography (TLC). Three different kinds of polystyrene (PS), i.e. PS grafted onto chitin, PS embedded in chitin and PS in grafting solution were gained. The variation of their molecular weight (MW) and width index of molecular weight distribution ( Mw/ Mn) determined by gel permeation chromatography (GPC) at different grafting conditions is discussed.

Pengfei, Liu; Maolin, Zhai; Jilan, Wu

2001-05-01

111

Synthesis and Characterization of Block-Graft Copolymers [poly(epichlorohydrin- b -styrene)- g -poly(methyl methacrylate)] by Combination of Activated Monomer Polymerization, NMP and ATRP  

Microsoft Academic Search

Summary  Synthesis of block-graft copolymers, namely poly(epichlorohydrin-b-styrene)-g-poly(methyl methacrylate) (PECH-b-St)-g-PMMA) by combination of Activated Monomer (AM), Nitroxide Mediated Polymerization (NMP) and Atom Transfer Radical Polymerization\\u000a (ATRP) methods was described. For this purpose, first epichlorohydrin (ECH) was polymerized by using BF3THF complex in the presence of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyl-1-oxy (HTEMPO) via AM mechanism. The resulting\\u000a stable radical terminated polymer was subsequently used as a counter

M. Atilla Tasdelen; Yusuf Yagci; A. Levent Demirel; Tadeusz Biedron; Przemyslaw Kubisa

2007-01-01

112

Radiation-induced grafting of vinylbenzyl chloride onto a poly(ether ether ketone) film  

NASA Astrophysics Data System (ADS)

In this study, the effects of various irradiation conditions including solvent, monomer concentration, total dose, and dose rate on the radiation grafting of a VBC monomer onto a PEEK aromatic hydrocarbon film for the preparation of a PVBC-grafted PEEK (PEEK-g-PVBC) film were investigated. The results show that the desired PVBC-grafted PEEK film can be prepared using a simultaneous irradiation grafting method, and that the degree of grafting (DOG) of the film is largely influenced by the irradiation conditions. Among the applied solvents, halogenated solvents, dichloromethane and chloroform, were found to be suitable for grafting. The successful preparation of the grafted film was confirmed using analytical instruments such as FT-IR, TGA, and SEM-EDX.

Hwang, Mi-Lim; Song, Ju-Myung; Ko, Beom-Seok; Sohn, Joon-Yong; Nho, Young-Chang; Shin, Junhwa

2012-06-01

113

Usefulness of microporous hydrophobic polypropylene membranes after plasma-induced graft polymerization of acrylic acid for high-power nickel–cadmium batteries  

Microsoft Academic Search

Commercial microporous polypropylene (PP) membranes were modified by plasma-induced graft polymerization of acrylic acid (AAc) under UV irradiation. Under optimized conditions obtained membranes are hydrophilic and may be serviceable as separator in nickel–cadmium cell. Electrolytic resistance of modified membranes is evaluated and compared with that of commercial separators: conventional cellophane separation and hydrophilic polypropylene separation (Celgard 3501). This paper reports

Aleksander Ciszewski; Jerzy Kunicki; Irena Gancarz

2007-01-01

114

Grafting of poly(ethylene glycol) monoacrylates on polycarbonateurethane by UV initiated polymerization for improving hemocompatibility.  

PubMed

Poly(ethylene glycol) monoacrylates (PEGMAs) with a molecular weight between 400 and 1,000 g mol(-1) were grafted by ultraviolet initiated photopolymerization on the surface of polycarbonateurethane (PCU) for increasing its hydrophilicity and improving its hemocompatibility. The surface-grafted PCU films were characterized by Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle, scanning electron microscopy (SEM) and atomic force microscopy measurements. The surface properties of the modified films were studied in dry and wetted state. Blood compatibility of the surfaces was evaluated by platelet adhesion tests and adhered platelets were determined by SEM. The results showed that the hydrophilicity of the films had been increased significantly by grafting PEGMAs, and platelets adhesion onto the film surface was obviously suppressed. Furthermore, the molecular weight of PEGMAs had a great effect on the hydrophilicity and hemocompatibility of the PCU films after surface modification and increased with increasing molecular weight of PEGMAs. PMID:22661245

Feng, Yakai; Zhao, Haiyang; Behl, Marc; Lendlein, Andreas; Guo, Jintang; Yang, Dazhi

2013-01-01

115

Radiation Graft Copolymerization of Methacrylic Acid (MAA) onto Sago Starch Films  

Microsoft Academic Search

In this work, the factors that may affect the gamma radiation-induced grafting of methacrylic acid monomer (MAA) onto sago starch films were investigated. The graft copolymers were characterized by tensile mechanical testing, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and infrared spectroscopy. The results showed that the highest grafting yield was obtained within the irradiation dosage level of 10–20 kGy

M. M. Senna; Khairul Zaman; Zulkafli Ghazali; Kamaruddin Hashim

2005-01-01

116

Electrodialysis of Sulfuric Acid with Cation-Exchange Membranes Prepared by Electron-Beam-Induced Graft Polymerization  

NASA Astrophysics Data System (ADS)

Strongly acidic cation-exchange membranes were prepared by the electron-beam-induced graft polymerization of glycidyl methacrylate onto a high-density polyethylene film with a thickness of 35 ?m and the subsequent conversion of the resulting epoxy group into a sulfonic acid group. The resulting cation-exchange membranes with various ion-exchange capacities or sulfonic acid group densities ranging from 1.9 to 2.7 mmol/g were applied to the enrichment of 0.50 mol/L sulfuric acid by electrodialysis. Concentrated sulfuric acids at concentrations of 1.4 to 2.9 mol/L were obtained in the concentrate chamber during the electrodialysis operated at 30 mA/cm2 and 298 K, using a pair of this cation-exchange membrane and a commercially available anion-exchange membrane.

Asari, Yuki; Shoji, Nobuyoshi; Miyoshi, Kazuyoshi; Umeno, Daisuke; Saito, Kyoichi

117

Fabrication of conducting poly(3-thiophene boronic acid)-grafted multi-walled carbon nanotubes by oxidative polymerization.  

PubMed

Composite materials of multi-walled carbon nanotubes (MWNTs) and a conducting polymer, poly(3-thiophene boronic acid) (PTBA) were prepared by in-situ oxidative polymerization of TBA in the presence of MWNTs and potassium dichromate. The MWNTs which were previously surface functionalized with acid chloride groups were reacted with TBA using a simple "chemical grafting" technique. It was observed that the nanotubes were dispersed uniformly in the pi-conjugated polymer matrix and entrapped by the polymer. The conductivity of the composites was higher than that of the pure polymer from a conventional four-probe technique, which indicates that the fabrication of MWNTs into the polymer matrix significantly improves the conductivity of the polymer due to the intrinsic properties of MWNTs. PMID:22524052

Niranjanmurthi, Lingappan; Choi, Byung Chun; Park, Jong Myung; Lim, Kwon Taek

2012-01-01

118

Polymer Grafting of Carbon Nanotubes Using Living Free?Radical Polymerization  

Microsoft Academic Search

The chemistry of carbon nanotubes has become an area of intense research as chemical derivatization is the only means for modifying the properties of these highly interesting and technologically promising materials. Specifically, numerous researchers have focused on improving the solubility of carbon nanotubes through chemical grafting. To this end, significant recent effort has been devoted to the attachment of polymers

Christa M. Homenick; Gregor Lawson; Alex Adronov

2007-01-01

119

Conductive surface via graft polymerization of aniline on a modified glass surface  

Microsoft Academic Search

A functionalization with an aniline monolayer of a modified glass surface, followed by the surface grafting of polyaniline (PANI) was used to prepare a conductive surface. A bromopropylsilane monolayer was first generated by reacting a hydroxylated surface with 3-bromopropyltrichlorosilane under an inert atmosphere. This layer was functionalized by its reaction with aniline, which substituted the bromide atoms of the silane

Z. F. Li; E. Ruckenstein

2002-01-01

120

In vitro release studies of vitamin B 12 from poly N-vinyl pyrrolidone/starch hydrogels grafted with acrylic acid synthesized by gamma radiation  

NASA Astrophysics Data System (ADS)

Co-polymeric hydrogels containing N-vinyl pyrrolidone and starch grafted with acrylic acid were synthesized by gamma radiation to be used as drug delivery system. Their gel contents, grafting swelling and thermal gravimetric analysis were evaluated. The gel content increases by increasing the irradiation dose up to 50 kGy, then decreases. The grafting percent increases by the increasing of acrylic acid. The thermal stability and the rate of the thermal decomposition changed according to the different compositions. The maximum rate of the thermal decomposition decreases by increasing the irradiation dose from 20 to 30 kGy and increases by increasing the irradiation dose from 30 to 70 kGy. The hydrogels loaded with vitamin B 12 demonstrated a decrease release in acidic medium than the neutral one.

Eid, M.

2008-12-01

121

Functionalization of nanochannels by radio-induced grafting polymerization on PET track-etched membranes  

NASA Astrophysics Data System (ADS)

The application of swift-heavy ion bombardment to polymers is a well-established technique to manufacture micro- and nanopores onto polymeric films to obtain porous membranes. A few years ago, it was realized that, during ion bombardment, the high energy deposition along the ion path through the polymer reached cylindrical damage regions corresponding to the core trace and the penumbra. After the etching procedure, there are still enough active sites left in the penumbra that can be used to initiate a polymerization process selectively inside the membrane pores.

Soto Espinoza, S. L.; Arbeitman, C. R.; Clochard, M. C.; Grasselli, M.

2014-01-01

122

Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane surface with stably anti-protein-fouling performance via a two-step surface polymerization  

NASA Astrophysics Data System (ADS)

A zwitterionic polymer, poly(3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide) (poly(MPDSAH)) was successfully grafted in high density from the surface of poly(vinylidene fluoride) (PVDF) hollow fiber membrane via a two-step polymerization. Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) chains were firstly grafted from outside surface of PVDF membrane through atom transfer radical polymerization (ATRP) to provide the initiation sites for subsequent cerium (Ce (IV))-induced graft copolymerization of polyMPDSAH in the presence of N,N'-ethylene bisacrylamide (EBAA) as a cross-linking agent. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) confirmed that the EBAA could stimulate zwitterionic polymers grafting onto the membrane surface. The dense poly(MPDSAH) layers on the PVDF membrane surface were revealed by the scanning electron microscope (SEM). The mechanical property of PVDF membrane was improved by the zwitterionic surface layers. The gravimetry results indicated the grafting amount increased to 520 ?g/cm2 for a copolymerization time of more than 3 h. Static and dynamic water contact angle measurements showed that the surface hydrophilicity of the PVDF membranes was significantly enhanced. As the grafting amount reached 513 ?g cm-2, the value of contact angle dropped to 22.1° and the amount of protein adsorption decreased to zero. The cyclic experiments for BSA solution filtration demonstrated that the extent of protein fouling was significantly reduced and most of the fouling was reversible. The grafted polymer layer on the PVDF membrane showed a good stability during the membrane cleaning process. The experimental results concluded a good prospect in obtaining the sulfobetaine-modified PVDF membranes with high mechanical strength, good anti-protein-fouling performance, and long-term stability via the two-step polymerization.

Li, Qian; Bi, Qiu-Yan; Zhou, Bo; Wang, Xiao-Lin

2012-03-01

123

Radiation Grafting of Acrylonitrile onto Polyester Fiber as the Reinforcing Filler for Poly (Vinyl Chloride).  

National Technical Information Service (NTIS)

Studies have been carried out on radiation-induced grafting of acrylonitrile onto polyester fiber and on the properties of the grafted fiber in an attempt to increase the strength of polyester fiber reinforced soft poly (vinyl chloride) (PVC) sheet by imp...

K. Kaji, I. Ando

1985-01-01

124

Stearyl methacrylate-grafted-chitosan nanoparticle as a nanofiller for PLA: Radiation-induced grafting and characterization  

NASA Astrophysics Data System (ADS)

This paper reports a one-pot synthesis using radiation-induced grafting technique to modify biopolymer-based chitosan nanoparticles as a nanofiller for blending with poly(lactic acid) (PLA). Hydrophobic stearyl methacrylate (SMA) was grafted onto non-irradiated chitosan (CS0) and pre-irradiated chitosan with a ?-ray dose of 40 kGy (CS40) to obtain stearyl methacrylate-grafted-chitosan nanoparticles (SMA-g-CSNPs).The effects of the pre-irradiated CS, grafting doses and SMA concentrations on degree of grafting (DG) and particle formation were studied. FT-IR and XRD were used to characterize the chemical and packing structure of SMA-g-CSNPs. The particle formulation and size of SMA-g-CSNPs were observed by TEM and AFM. The spherical core-shell SMA-g-CSNPs with the size ranging from 50 to 140 nm were successfully prepared. The SMA-g-CSNPs from CS40 has higher DG and smaller particle size when compared with CS0. The SMA-g-CSNPs are able to improve the compatibility between CS and PLA.

Rattanawongwiboon, Thitirat; Haema, Kamonwon; Pasanphan, Wanvimol

2014-01-01

125

Plasma-induced graft co-polymerization of acrylic acid onto the polyurethane surface  

Microsoft Academic Search

We introduced carboxylic groups on the surface of polyurethane (PU) with the aid of oxygen plasma treatment and the post-grafting of acrylic acid (AAc) in an aqueous solution. After plasma treatment, PU was exposed to the air to generate peroxides. Peroxides were confirmed by the 1,1-diphenyl-2-picrylhydrazyl method. We chose different parameters of plasma treatment to get the optimum condition for

Ho-Suk Choi; Young-Sun Kim; Yan Zhang; Shen Tang; Sung-Woon Myung; Byung-Cheol Shin

2004-01-01

126

Radiation synthesis of chitosan beads grafted with acrylic acid for metal ions sorption  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of acrylic acid onto chitosan beads was performed in solution at a dose rate of 20.6 Gy/min of cobalt-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted material was performed by FTIR spectroscopy and the swelling measurements at different pHs. The grafting yield increased with the increase in dose, it reached 80% at 40 kGy irradiation dose. The removal of Pb and Cd ions from aqueous solutions was investigated with both ungrafted and grafted chitosan beads. The sorption behavior of the sorbents was examined through pH, kinetics and equilibrium measurements. Grafted chitosan beads presented higher sorption capacity for both metal ions than unmodified chitosan beads.

Benamer, S.; Mahlous, M.; Tahtat, D.; Nacer-Khodja, A.; Arabi, M.; Lounici, H.; Mameri, N.

2011-12-01

127

Surface studies of radiation grafted sulfonic acid membranes: XPS and SEM analysis  

NASA Astrophysics Data System (ADS)

PTFE-g-polystyrene sulfonic acid membranes prepared by radiation-induced graft copolymerization of styrene onto poly(tetrafluoroethylene) (PTFE) films followed by sulfonation reactions were investigated with respect to their morphology and surface chemical properties. The chemical composition of the membranes surfaces was monitored at various degrees of grafting using X-ray photoelectron spectroscopy (XPS). Considerable differences in the concentration of the chemical components of the surfaces were observed despite the predominance of all membranes surfaces by a hydrocarbon fraction originated from the incorporated sulfonated polystyrene grafts. The distribution of the sulfonated polystyrene grafts in membranes having various degrees of grafting was investigated by scanning electron microscopy (SEM). The membranes achieved a homogenous distribution at degrees of grafting of 24% and above. The results of this work suggest that the membranes have a chemically sensitive surfaces and this is most likely to have an impact on their interfacial properties and chemical stability.

Nasef, Mohamed Mahmoud; Saidi, Hamdani

2006-02-01

128

Surface-initiated Ring-opening Metathesis Polymerization in the Vapor Phase: An Efficient Method for Grafting Cyclic Olefins of Low Strain Energies  

PubMed Central

Surface grafting of cyclic olefins with low strain energies, including cyclopentene (CP), 1,4-cyclohexadiene (CHD), cycloheptene (CHP), cis-cyclooctene (CO), cis,cis-1,5-cyclooctadiene (COD), 1,3,5,7-cyclooctatetraene (COT), cyclododecene (CD), and trans,trans,cis-1,5,9-cyclododecatriene (CDT), were explored using ring-opening metathesis polymerization in the vapor phase. These monomers do not polymerize when SiROMP is carried out in solution due to pronounced chain transfer on surfaces where chains are in close proximities. In the vapor phase, however, chain transfer is suppressed at the solid-vapor interfaces, which permits the polymerization of most of these monomers. A minimal required strain energy of 2.2 kcal/mol was determined in this study, which is significantly lower than the estimated 13.3 kcal/mol for SiROMP carried out in solution, indicating that the enhancement in monomer polymerizability is significant using the vapor phase approach. A series of polyalkenamers with controlled fraction of unsaturation from 8% to 50% along the polymer backbone were grafted to solid substrates. It was observed that the logarithm of largest grafted layer thickness obtained before the removal of chain transfer products – which correlates with the extent of polymerization – scales with monomer strain energy. This confirms that the release of ring strain is the thermodynamic driving force for SiROMP. It was also found that although chain transfer is suppressed in the vapor phase, it is important in monomer/polymer systems where the fraction of unsaturated bonds is high. In these cases, grafted polymer thickness is dominated by chain transfer, rather than by monomer strain energy. A quantitative relationship is established for estimating graft thickness of a particular monomer using its strain energy and fraction of unsaturated bonds in the monomer. PMID:21469729

Lerum, Maria Felisa Z.; Chen, Wei

2011-01-01

129

Development of functional adsorbent from PU foam waste via radiation induced grafting I: Process parameter standardization  

NASA Astrophysics Data System (ADS)

Mutual radiation grafting process has been used to covalently link polymer chains of poly(acrylic acid) to polyurethane foam waste using 60Co-gamma radiation source. Various experimental parameters were investigated in order to optimize the grafting process. The grafted samples have been characterized for water-uptake, surface morphology and thermal stability. Grafting extent increased with dose, dose rate and monomer concentration but decreased with increase in density of PU foam. The matrix grafted up to an extent of ˜90% showed uptake capacity of 220 mg/g (0.09 mol of dye/mol of acrylic acid) for a monovalent dye (basic red 29) within 3 h of contact time in a batch process.

Goel, N. K.; Kumar, Virendra; Dubey, K. A.; Bhardwaj, Y. K.; Varshney, L.

2013-01-01

130

Functionalization of polymer surfaces by radiation-induced grafting for separation of heavy metal ions  

NASA Astrophysics Data System (ADS)

The reported investigations were focused on the elucidation of the most important factors influencing radiation-induced grafting, particularly on studying the relationship between layer structure formed via copolymerization and content of monomers in the initial solution. Sorption capacity of the prepared by radiation grafting adsorber was evaluated by gamma radiometer using 152Eu3+ as a marker monitoring depletion of the radioisotope from the feed solution.

Kornacka, E. M.; Przybytniak, G.; Fuks, L.; Walo, M.; ?yczko, K.

2014-01-01

131

TEMPO addition into pre-irradiated fluoropolymers and living-radical graft polymerization of styrene for preparation of polymer electrolyte membranes  

NASA Astrophysics Data System (ADS)

We prepared proton exchange membranes (PEMs) by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO)-mediated living-radical graft polymerization (LRGP) of styrene into fluoropolymer films and subsequent sulfonation. Poly(vinylidene fluoride) (PVDF) and poly(ethylene- co-tetrafluoroethylene) (ETFE) films were first irradiated and then treated with TEMPO solutions in various solvents. TEMPO addition was confirmed by the test of styrene grafting into TEMPO-treated films at 60 °C, at which the LRGP never proceeds. This test enabled us to differentiate the LRGP from the conventional graft polymerization. In order to gain a deep insight about TEMPO-addition reaction, the TEMPO-penetration behavior into the base polymer films was examined by a permeation experiment and computer simulation. Xylene and dioxane were appropriate solvents for the complete introduction of TEMPO into PVDF and ETFE films, respectively. Then, the LRGP of styrene was performed based on the fully TEMPO-capped films at 125 °C with various solvents. By using an alcoholic solvent, the degree of grafting was enhanced and it reached a maximum of 38%. This grafted film was sulfonated to prepare a PEM showing an ion exchange capacity of 2.2 meq/g and proton conductivity of 1.6×10 -1 S/cm.

Sawada, Shin-ichi; Suzuki, Akihiro; Terai, Takayuki; Maekawa, Yasunari

2010-04-01

132

Mechanical properties of radiation-sterilised human Bone-Tendon-Bone grafts preserved by different methods.  

PubMed

Patellar tendon auto- and allo-grafts are commonly used in orthopedic surgery for reconstruction of the anterior cruciate ligaments (ACL). Autografts are mainly used for primary reconstruction, while allografts are useful for revision surgery. To avoid the risk of infectious disease transmission allografts should be radiation-sterilised. As radiation-sterilisation supposedly decreases the mechanical strength of tendon it is important to establish methods of allograft preservation and sterilisation assuring the best quality of grafts and their safety at the same time. Therefore, the purpose of this study was to compare the tensile strength of human patellar tendon (cut out as for ACL reconstruction), preserved by various methods (deep fresh freezing, glycerolisation, lyophilisation) and subsequently radiation-sterilised with doses of 0, 25, 50 or 100 kGy. Bone-Tendon-Bone grafts (BTB) were prepared from cadaveric human patella tendons with both patellar and tibial attachments. BTB grafts were preserved by deep freezing, glycerolisation or lyophilisation and were subsequently radiation-sterilised with doses of 0 (control), 25, 50 or 100 kGy. All samples were subjected to mechanical failure tensile tests with the use of Instron system in order to estimate their mechanical properties. All lyophilised grafts were rehydrated before performing of those tests. Obtained mechanical tests results of examined grafts suggest that deep-frozen irradiated grafts retain their initial mechanical properties to an extent which does not exclude their clinical application. PMID:18982427

Kami?ski, A; Gut, G; Marowska, J; Lada-Koz?owska, M; Biwejnis, W; Zasacka, M

2009-08-01

133

IMPROVED DIELECTRICS PRODUCED BY MEANS OF HIGH-ENERGY RADIATION  

Microsoft Academic Search

An outline is given of production of solid dielectrics by radiation ; polymerization, and of specialized techniques such as encapsulation of components ; by radiation polymerization and adhesion by graft polymerization. The ; modification of dielectrics is summarized, with attention to such examples as the ; radiation cross-linking of elastomers to give form-stable rubber-like resilient ; materials that are insoluble

Waddington

1961-01-01

134

Synthesis and polymerization of a radiation curable hyperbranched resin based on epoxy functional fatty acids  

Microsoft Academic Search

A radiation curable resin has been synthesized from a hydroxy functional hyperbranched polyether onto which an epoxy functional fatty acid, vernolic acid, has been attached. The resin was cationically polymerized in presence of different amounts of vernolic acid methyl ester as a reactive diluent. The coating mixtures contained up to 30wt.% methyl ester and all formulations polymerized readily and formed

Johan Samuelsson; Per-Erik Sundell; Mats Johansson

2004-01-01

135

Effects of triphenylsulfonium hexafluorophosphate in the radiation-induced cationic polymerization of styrene  

Microsoft Academic Search

Radiation-induced cationic polymerization of styrene was studied in methylene chloride in the presence of triphenylsulfonium hexafluorophosphate. Acceleration in polymerization and an increase in molecular weight at a low temperature (- 78°C) were observed in the presence of triphenylsulfonium salt. A study of pulse radiolysis revealed that both effects are due mainly to PFâ⁻, which forms ion pairs with the cationic

Soukil Mah; Yukio Yamamoto; Koichiro Hayashi

1982-01-01

136

Synthesis, modification and graft polymerization of magnetic nano particles for PAH removal in contaminated water  

PubMed Central

Magnetic nanoparticles (MNPs) were modified with 3-Mercaptopropytrimethoxysiline (MPTMS) and grafted with allyl glycidyl ether for coupling with beta naphtol as a method to form a novel nano-adsorbent to remove two poly aromatic hydrocarbons (PAHs) from contaminated water. The modified MNPs were characterized by transmission electron microscopy, infrared spectroscopy and thermogravimetric analysis. Results showed that the modified MNPs enhanced the process of adsorption. Tests were done on the adsorption capacity of the two PAHs on grafted MNPs; factors applied to the tests were temperature, contact time, pH, salinity and initial concentration of PAHs. Results revealed that adsorption equilibrium was achieved in 10 min, and the maximum adsorption capacity was determined as 4.15 mg/g at pH?=?7.0 and 20°C. The equilibrium adsorption data of the two PAHs by the modified MNPs were analyzed by Langmuir, Freundlich and Temkin models. Equilibrium adsorption data was determined from the Langmuir, Freundlich and Temkin constants from tests under conditions of pH?=?7 and temperature 20°C. Analysis of the adsorption-desorption process indicated that the modified MNPs had a high level of stability and good reusability. Magnetic separation in these tests was fast and this shows that the modified MNPs have great potential to be used as a new adsorbent for the two PAHs removal from contaminated water in water treatment. PMID:25101170

2014-01-01

137

Polymer-grafted silica: A screening system for polymeric adsorption resin development  

SciTech Connect

A screening-level methodology was developed for the evaluation of solute affinity for polymers that are candidate sorption resins. In this approach novel grafted polymer-silica resins were synthesized to produce poly(vinylpyrrolidone)-silica (PVP-Si) and poly(vinyl acetate)-silica (PVAc-Si) resins. The polymer-silica resins along with a number of commercially available polymer resins were used to evaluate the aqueous-phase adsorption of phenol, tetrachloroethene (PCE), trichloroethene (TCE), and chloroform. The polymer-grafted silicas were able to selectively remove pollutants from water with a covalently bonded polymer layer that has a high affinity for the target pollutant. The PVAc-silica resin had a sorption capacity for TCE and CHCl[sub 3] as high as commercial poly(styrene) resin XAD-4; the PVP-Si resin had a sorption capacity for phenol higher than a commercial poly-(vinylpyridine) resin (Reillex 425). PCE adsorption onto the PVAc-silica was comparable to the commercial poly(methacrylate) and poly(vinylpyridine) resins but less than the poly(styrene) resin. The results show that the Hildebrand solubility parameter along with the dipole moment of the polymer functional groups can be used for an initial screening-level assessment of polymer-solute affinity.

Browne, T.E.; Cohen, Y. (Univ. of California, Los Angeles (United States))

1993-04-01

138

Bioresponse to polymeric substrates: Effect of surface energy, modulus, topography, and surface graft copolymers  

NASA Astrophysics Data System (ADS)

Biofouling is the accumulation of biological matter on a substrate. It is essential to elucidate and model the major factors that affect both biological settlement and adhesion to substrates in order to develop coatings that minimize initial fouling or ease the removal of this fouling. To date, models that have estimated adhesion strength to coatings primarily included bulk elastic modulus and surface energy. Topography, however, has been found to dominate both these terms in the reduction of settlement and has been found to affect the adhesion strength as well. Silicone foul release coatings have demonstrated moderate success in the prevention of marine biofouling because of their low modulus and low surface energy. Problems exist with durability and eventual fouling of the coating due to the overgrowth of foulants that prefer hydrophobic substrates. This research details the characterization and the surface and bulk modification of a commercially available silicone elastomer. The modifications include bulk additives, surface topography, and surface graft copolymers. The effect of these modifications on biological response was then assayed using the alga Ulva as a model for marine biofouling. The unmodified silicone elastomer has a bulk modulus of approximately 1 MPa. The addition of vinyl functional polydimethylsiloxane oils allowed for a greater than 200% increase or a 90% decrease in the bulk modulus of the material. The addition of non-reactive polydimethylsiloxane oils allowed for a change in the surface lubricity of the elastomer without a significant change in the mechanical properties. Topographical modifications of the surface show a profound effect on the bioresponse. Appropriately scaled engineered microtopographies replicated in the silicone elastomer can produce a 250% increase in algal zoospore fouling or an 85% reduction in settlement relative to a smooth silicone elastomer. Finally, the modification of the surface energy of this material was achieved by acid catalyzed surface hydrolysis and subsequent grafting of poly(ethylene glycol), polysulfone, or perfluoropolyether. The water contact angle could be increased by 16% or decreased by 60% relative to the silicone elastomer control. These surfaces were characterized by various contact angle techniques, ATR-FTIR, and XPS. These surface grafts were also combined with the topographical modifications to evaluate the relative significance of these two factors on bioresponse.

Wilson, Leslie Hoipkemeier

139

Analysis of a flexible polymeric film with imbedded micro heat pipes for spacecraft radiators  

E-print Network

radiators are being developed to accommodate deployment mechanisms. An analytical model suggests that a lightweight polymeric material with imbedded micro heat pipe arrays can meet heat dissipation requirements while contributing less mass than competing...

McDaniels, Deborah Marie

2012-06-07

140

New Applications of Ring-Opening Metathesis Polymerization for Grafting Alkylene Oxide-Based Copolymers  

NASA Astrophysics Data System (ADS)

This research tackles the challenges of innovative modification of poly(allyl alkylene oxides) by ROMP to produce new materials. Firstly, binary and ternary copolymers, poly(epichlorohydrin-allyl glycidyl ether) (ECH-AGE) and poly (epichlorohydrin-propylene oxide-allyl glycidyl ether) (ECH-PO-AGE), have been prepared using as initiator a catalytic system consisting of an alkyl aluminium, controlled amounts of water and different compounds (ethers, diols, phosphines, salicylic acid derivatives, organozincs) acting as cocatalysts. Among catalysts explored in these copolymerizations most productive showed to be the systems triisobutylaluminium (TIBA), water and Zn(DIPS)2 or Zn(acac)2. Copolymers which have become thus available were subsequently grafted onto the pendent allylic groups by ROMP with cycloolefins (cyclooctene, norbornene, cyclododecene) involving ruthenium based catalysts.

Spurcaciu, Bogdan; Buzdugan, Emil; Nicolae, Cristian; Ghioca, Paul; Iancu, Lorena; Dragutan, Valerian; Dragutan, Ileana

141

Surface nano-structuring of reverse osmosis membranes via atmospheric pressure plasma-induced graft polymerization for reduction of mineral scaling propensity  

Microsoft Academic Search

Surface nano-structuring of polyamide desalination membrane with a hydrophilic poly(methacrylic acid) was shown to reduce the membrane mineral scaling propensity as demonstrated with calcium sulfate dihydrate (gypsum). A two-step approach was employed, whereby the active polyamide (PA) layer of a thin-film composite (TFC) synthesized membrane was activated with impinging atmospheric plasma, followed by a solution free-radical graft polymerization (FRGP) of

Myung-man Kim; Nancy H. Lin; Gregory T. Lewis; Yoram Cohen

2010-01-01

142

Effects of photo-induced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine on physical properties of cross-linked polyethylene in artificial hip joints.  

PubMed

Osteolysis caused by wear particles from polyethylene in the artificial hip joints is a serious issue. We have used photo-induced radical graft polymerization to graft 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer onto the surface of cross-linked polyethylene (CLPE-g-MPC) in order to reduce friction and wear at the bearing surface of the joint. The physical and mechanical properties of CLPE and CLPE-g-MPC were not significantly different, expect that the friction coefficient of untreated CLPE cups was 0.0075, compared with 0.0009 for CLPE-g-MPC cup, an 88% reduction. After 3.0 x 10(6) cycles in the hip joint simulator test, we could not observe any wear of CLPE-g-MPC cups. We concluded that the advantage of photo-induced radical graft polymerization technique was that the grafted MPC polymer gave a high lubricity only on the surface and has no effect on the bulk properties of the CLPE substrate. PMID:17483881

Kyomoto, Masayuki; Moro, Toru; Konno, Tomohiro; Takadama, Hiroaki; Kawaguchi, Hiroshi; Takatori, Yoshio; Nakamura, Kozo; Yamawaki, Noboru; Ishihara, Kazuhiko

2007-09-01

143

Radiation grafted and sulfonated (FEP-g-polysterene) - An alternative to perfluorinated membranes for PEM fuel cells?  

Microsoft Academic Search

Partially fluorinated proton exchange membranes (PEMs) were synthesized for fuel cell applications by simultaneous radiation grafting of styrene on FEP films followed by sulfonation. Properties of the synthesized membranes can be tailored by varying the degree of grafting and crosslinking. The performance of these membranes was tested in H2\\/O2 fuel cells. Long time testing showed steady performance for high grafted

F. N. Buechi; B. Gupta; M. Rouilly; P. C. Hauser; A. Chapiro; G. G. Scherer

1992-01-01

144

The influence of crosslinker on the properties of radiation-grafted films and membranes based on ETFE  

Microsoft Academic Search

Crosslinked proton-exchange membranes were prepared by radiation-induced grafting of styrene into poly(ethylene-alt-tetrafluoroethylene) (ETFE) and subsequent sulfonation. The influence of the crosslinker, divinylbenzene (DVB), on various film and membrane properties was investigated in detail. A series of grafted films and membranes were prepared at varying DVB concentrations at a fixed graft level (?25%) for this purpose. Grafting kinetics and kinetic parameters,

Hicham Ben youcef; Selmiye Alkan Gürsel; Alexander Wokaun; Günther G. Scherer

2008-01-01

145

Application of Sepharose and Sephadex modified by means of radiation grafting in separation of biomolecules  

NASA Astrophysics Data System (ADS)

In this work Sepharose-NASI-BSA and Sephadex-NASI-BSA were prepared by means of pre-irradiation grafting and direct radiation grafting separately. The radiation grafting condition were given. In order to get those compounds the conjugation reaction between NASI and BSA was investigated as well. The reaction was performed at 37 °C for 2hs, but in the case of Sephadex-NASI, it took longer time, 6hs, to finish the conjugation reaction. The application of the radiation modified matrixes as a kind of filling materials of column chromatography in separation of D,L-tryptophans was studied. The results showed that this method was accessible after some improvements.

Li, Jun; Yi, Min; Ha, Hongfei

1995-02-01

146

Heterogenization of precious metal catalysts and enzymes by radiation-induced graft copolymerization. [Gamma or ultraviolet radiation  

SciTech Connect

The feasibility of using radiation graft copolymerization for the preparation of supports suitable for the heterogenization of catalysts was examined. To bind metal complexes, radiation graft copolymers of p-styryldiphenylphosphine with a number of trunk polymers were produced. Similarly enzyme immobilization was successful on chemically modified p-nitrostyrene copolymers. Conditions for ..gamma.. and/or UV radiation grafting of styrene, p-styryldiphenylphosphine, vinyldiphenylphosphine and p-nitrostyrene to a number of trunk polymers were established. New techniques to chemically modify styrene copolymers and to analyze the resultant catalysts were adapted from traditional methods. Procedures to assess the catalytic activity of the heterogenized catalysts were also developed from techniques used in conventional catalytic research.

Levot, R.G.

1983-01-01

147

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization  

PubMed Central

Summary The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a “grafting from” process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP. PMID:23946859

Moreira, Guillaume; Charles, Laurence; Major, Mohamed; Vacandio, Florence; Guillaneuf, Yohann

2013-01-01

148

Evaluation of graft stiffness using acoustic radiation force impulse imaging after living donor liver transplantation.  

PubMed

Acoustic radiation force impulse (ARFI) imaging is an ultrasound-based modality to evaluate tissue stiffness using short-duration acoustic pulses in the region of interest. Virtual touch tissue quantification (VTTQ), which is an implementation of ARFI, allows quantitative assessment of tissue stiffness. Twenty recipients who underwent living donor liver transplantation (LDLT) for chronic liver diseases were enrolled. Graft types included left lobes with the middle hepatic vein and caudate lobes (n = 11), right lobes (n = 7), and right posterior segments (n = 2). They underwent measurement of graft VTTQ during the early post-LDLT period. The VTTQ value level rose after LDLT, reaching a maximum level on postoperative day 4. There were no significant differences in the VTTQ values between the left and right lobe graft types. Significant correlations were observed between the postoperative maximum value of VTTQ and graft volume-to-recipient standard liver volume ratio, portal venous flow to graft volume ratio, and post-LDLT portal venous pressure. The postoperative maximum serum alanine aminotransferase level and ascites fluid production were also significantly correlated with VTTQ. ARFI may be a useful diagnostic tool for the noninvasive and quantitative evaluation of the severity of graft dysfunction after LDLT. PMID:25203425

Ijichi, Hideki; Shirabe, Ken; Matsumoto, Yoshihiro; Yoshizumi, Tomoharu; Ikegami, Toru; Kayashima, Hiroto; Morita, Kazutoyo; Toshima, Takeo; Mano, Yohei; Maehara, Yoshihiko

2014-11-01

149

Preparation and characterization of supported hydrogels obtained by radiation grafting of binary monomers  

NASA Astrophysics Data System (ADS)

The preparation and characterization of supported hydrogels obtained by radiation-induced graft copolymerization of styrene/maleic anhydride (Sty/MAn) binary monomers system onto low density polyethylene films were investigated. Attention was focused on the selection of the reaction parameters suitable for the commercial production of such hydrogels. The factors which affect the preparation process and grafting yield are type of solvent, dose rate, total dose, comonomer composition and their concentrations in the diluents. The structure and composition of the grafted chains were also determined. The change in tensile strength and percent elongation at break with degree of grafting was determined for the untreated LDPE-g-P(Sty/MAn) membranes. It was found that the tensile strength improved by grafting but the percent elongation decreased. The change in thermal parameters was measured using differential scanning calorimeter (DSC). The grafted P(Sty/MAn) chains are amorphous in nature and a slight effect on the crystallinity of PE structure was observed. The possibility of the practical uses of such modified membranes was suggested.

Hegazy, El-Sayed A.; Abd El-Rehim, H. A.; Khalifa, N. A.; El-Hag Ali, A.

1999-06-01

150

UV radiation induced surface modulation time evolution in polymeric materials  

NASA Astrophysics Data System (ADS)

The reorganization processes at submicron level of the polymeric materials have been investigated because of their applications in optoelectronics and bio-science. We have obtained surface relief modulation in single step processing on the photo resist and polysiloxane films. But for technical applications the time evolution and stability of the induced surface structure is an important parameter and is a problem to be discussed. In case of single step surface relief formation on polymeric materials the process is connected with the photochromic behavior of the materials. As it is known the UV light induced effects on the material structure are reversible under the action of visible light, but with different speeds. In this report is analyzed the time evolution of the surface modulation obtained under the action of the UV light for azopolymers with different structures.

Apostol, I.; Apostol, D.; Damian, V.; Iordache, I.; Hurduc, N.; Sava, I.; Sacarescu, L.; Stoica, I.

2010-11-01

151

Radiation induced grafting of some vinyl monomers on cotton fabric for improved properties. I—Grafting with styrene  

NASA Astrophysics Data System (ADS)

Cotton fabric has been grafted by styrene using the direct irradiation method. Mixture of toluene and methanol was used to dilute styrene in the grafting solution. The effect of irradiation dose, solvent, and monomer concentration were investigated. Crease recovery was measured as a function of the grafting percentage. It was found that the crease recovery shows a good improvement even at low grafting percentage. Grafted samples gained the ability to be dyed with disperse dyes. Grafted samples containing as low as 2.5% polystyrene show good affinity towards disperse dyes. Moreover, it shows a homogeneous distribution of the grafted chains through the fabric. The tensile properties of the grafted fabric was also measured as a function of the grafting percentage.

Zahran, A. H.; Dessouki, A. M.; Abo Zeid, M.

152

Mechanical properties of radiation-sterilised human Bone-Tendon-Bone grafts preserved by different methods  

Microsoft Academic Search

Patellar tendon auto- and allo-grafts are commonly used in orthopedic surgery for reconstruction of the anterior cruciate\\u000a ligaments (ACL). Autografts are mainly used for primary reconstruction, while allografts are useful for revision surgery.\\u000a To avoid the risk of infectious disease transmission allografts should be radiation-sterilised. As radiation-sterilisation\\u000a supposedly decreases the mechanical strength of tendon it is important to establish methods

A. Kami?ski; G. Gut; J. Marowska; M. ?ada-Koz?owska; W. Biwejnis; M. Zasacka

2009-01-01

153

Modeling and optimization aspects of radiation induced grafting of 4-vinylpyridene onto partially fluorinated films  

NASA Astrophysics Data System (ADS)

Modeling and optimization aspects of radiation induced grafting (RIG) of 4-vinylpyridine (4-VP) onto partially fluorinated polymers such as poly(ethylene-co-tetrafluoroethene) (ETFE) and poly(vinylidene fluoride) (PVDF) films were comparatively investigated using response surface method (RSM). The effects of independent parameters: absorbed dose, monomer concentration, grafting time and reaction temperature on the response, grafting yield (GY) were correlated through two quadratic models. The results of this work confirm that RSM is a reliable tool not only for optimization of the reaction parameters and prediction of GY in RIG processes, but also for the reduction of the number of the experiments, monomer consumption and absorbed dose leading to an improvement of the overall reaction cost.

Nasef, Mohamed Mahmoud; Ahmad Ali, Amgad; Saidi, Hamdani; Ahmad, Arshad

2014-01-01

154

Novel ETFE based radiation grafted poly(styrene sulfonic acid- co-methacrylonitrile) proton conducting membranes with increased stability  

Microsoft Academic Search

Styrene radiation grafted ETFE based proton conducting membranes are subject to degradation under fuel cell operating conditions and show a poor stability. Lifetimes exceeding 250h can only be achieved with crosslinked membranes. In this study, a novel approach based on the increase of the intrinsic oxidative stability of uncrosslinked membranes is reported. Hence, the co-grafting of styrene with methacrylonitrile (MAN),

Hicham Ben youcef; Lorenz Gubler; Selmiye Alkan Gürsel; Dirk Henkensmeier; Alexander Wokaun; Günther G. Scherer

2009-01-01

155

Self-assembly and graft polymerization route to Monodispersed Fe3O4@SiO2--polyaniline core-shell composite nanoparticles: physical properties.  

PubMed

This study describes the synthesis of monodispersed core-shell composites of silica-modified magnetic nanoparticles and conducting polyaniline by self-assembly and graft polymerization. Magnetic ferrite nanoparticles (Fe3O4) were prepared by coprecipitation of Fe+2 and Fe+3 ions in alkaline solution, and then silananized. The silanation of magnetic particles (Fe3O4@SiO2) was carried out using 3-bromopropyltrichlorosilane (BPTS) as the coupling agent. FT-IR spectra indicated the presence of Fe--O--Si chemical bonds in Fe3O4@SiO2. Core-shell type nanocomposites (Fe3O4@SiO2/PANI) were prepared by grafting polyaniline (PANI) on the surface of silanized magnetic particles through surface initiated in-situ chemical oxidative graft polymerization. The nanocomposites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Fourier transform infrared (FTIR) spectra, UV-visible spectroscopy, photoluminescence (PL) spectra, electrical conductivity and magnetic characteristics. HRTEM images of the nanocomposites revealed that the silica-modified magnetic particles made up the core while PANI made up the shell. The XPS spectrum revealed the presence of silica in the composites, and the XRD results showed that the composites were more crystalline than pure PANI. PL spectra show that composites exhibit photoluminescent property. Conductivity of the composites (6.2 to 9.4 x 10(-2) S/cm) was higher than that of pristine PANI (3.7 x 10(-3) S/cm). The nanocomposites exhibited superparamagnetism. Formation mechanism of the core-shell structured nanocomposites and the effect of modified magnetic nanoparticles on the electro-magnetic properties of the Fe3O4@SiO2/PANI nanocomposites are also investigated. This method provides a new strategy for the generation of multi-functional nanocomposites that composed of other conducting polymers and metal nanoparticles. PMID:19198281

Reddy, Kakarla Raghava; Lee, Kwang-Pill; Kim, Ju Young; Lee, Youngil

2008-11-01

156

Hydrogels obtained by radiation-induced polymerization as delivery systems for peptide and protein drugs  

NASA Astrophysics Data System (ADS)

The controlled release of peptides and proteins from hydrogels obtained by radiation-induced polymerization of 2-hydroxyethyl methacrylate at a low temperature was studied. It was found that the extent of release progressively decreased as protein molecular weight increased until no further release occurred above a critical value of the latter. However, an increasing rate of protein release was found if the polymerization was carried out in the presence of poly(ethylene glycol), PEG. Moreover, only with high molecular weight PEGs were large proteins released. The release data as a function of swellability and porosity of polymer matrices were discussed.

Carenza, M.; Lora, S.; Caliceti, P.; Schiavon, O.; Veronese, F. M.

1993-10-01

157

Preparation and characterization of a magneto-polymeric nanocomposite: Fe 3O 4 nanoparticles in a grafted, cross-linked and plasticized poly(vinyl chloride) matrix  

NASA Astrophysics Data System (ADS)

In this work two kind of materials: (1) grafted, cross-linked and plasticized poly(vinyl chloride) (PVC) "plastic films" and (2) magnetic plastic films "magneto-polymeric nanocomposites" were prepared. Precursor solutions or "plastisols" used to obtain the plastic films were obtained by mixing PVC (emulsion grade) as polymeric matrix, di(2-ethylhexyl)phthalate (DOP) as plasticizer, a thermal stabilizer based in Ca/Zn salts, and a cross-linking agent, 3-mercaptopropyltrimethoxysilane (MTMS) or 3-aminopropyltriethoxysilane (ATES), at several concentrations. Flexible films were obtained from the plastisols using static casting. The stress-strain behavior and the gel content (determined by Soxhlet extraction with boiling THF) of the flexible films were measured in order to evaluate the effect of the cross-linking agent and their content on the degree of cross-linking. The magneto-polymeric nanocomposites were obtained by mixing the optimum composition of the plastisols (analyzed previously) with magnetite (Fe 3O 4)-based ferrofluid and DOP. Later, flexible films were obtained by static casting of the plastisol/ferrofluid systems. The magnetic films were characterized by the above-mentioned techniques and X-ray diffraction, vibrating sample magnetometry and thermogravimetrical analysis.

Rodríguez-Fernández, Oliverio S.; Rodríguez-Calzadíaz, C. A.; Yáñez-Flores, Isaura G.; Montemayor, Sagrario M.

158

On the mechanism of radiation-induced polymerization of vinyl monomers in ionic liquid  

NASA Astrophysics Data System (ADS)

An attempt was made to investigate the mechanism controlling the radiation-induced polymerization of vinyl monomers in room temperature ionic liquids. For that purpose, copolymerization of styrene (St) and methyl methacrylate (MMA) was initiated by 60Co gamma radiation in a moisture-stable ionic liquid, [choline chloride][ZnCl 2], and its mixture with THF (4:1 v/v). By analyzing the product composition with FTIR for a series of poly(St-co-MMA) samples, it was found that the mole fraction of St in the copolymer is linearly proportional to the mole fraction of St in the feed. Therefore, radiation polymerization in ionic liquid and its mixture with organic solvent is suggested to be a radical propagating process.

Liu, Yaodong; Wu, Guozhong

2005-06-01

159

Swelling characteristics of konjac glucomannan superabsobent synthesized by radiation-induced graft copolymerization  

NASA Astrophysics Data System (ADS)

Graft copolymerization of konjac glucomannan (KGM) and acrylic acid was induced by 60Co-? irradiation at room temperature. The effects of radiation dose and monomer-to-KGM ratio on grafting yield and equilibrium water absorbency were investigated. The KGM-based superabsorbent polymer (KSAP) could absorb water 625 times of its dry weight when the radiation dose was 5.0 kGy and monomer-to-KGM ratio was 5. The structure of KSAP was characterized by FTIR, XRD, and SEM. KSAP showed a lower crystallinity than KGM. The porous microstructure of KSAP was revealed by SEM. The diffusion mechanism of water in the hydrogel is consistent with the anomalous diffusion model. Cations, especially multivalent cations, greatly reduced water absorbency of KSAP. Rising temperature, acidic or basic solutions are not favorable for the swelling of KSAP.

Wu, Jia; Deng, Xiao; Lin, Xiangyang

2013-02-01

160

Chemical and radiation crosslinked polymer electrolyte membranes prepared from radiation-grafted ETFE films for DMFC applications  

Microsoft Academic Search

To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell (DMFC), doubly crosslinked membranes were prepared by chemical crosslinking using bifunctional monomers, such as divinylbenzene (DVB) and bis(p,p-vinyl phenyl) ethane (BVPE), and by radiation crosslinking. The membranes were prepared by grafting of m,p-methylstyrene (MeSt) and p-tert-butylstyrene (tBuSt) into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent

Jinhua Chen; Masaharu Asano; Tetsuya Yamaki; Masaru Yoshida

2006-01-01

161

Polymer monoliths synthesized by radiation co-polymerization in solution  

NASA Astrophysics Data System (ADS)

Hydrophilic co-polymer monoliths were prepared by irradiating alcoholic solutions containing diethyleneglycol dimethacrylate (DEGDMA) and 2-hydroxyethylacrylate (HEA) monomers. The effect of monomer ratio, solvent properties and radiation dose on the porous properties of the monoliths was studied in detail and compared to the monolith prepared from DEGDMA. Increase of the HEA content in the co-monomer mixture (up to 18 vol%) resulted in monoliths with increased pore size and hydrophilic character. The biggest pores were obtained when methanol was used as solvent. The use of the monoliths as chromatographic columns for separation of proteins, amino and nucleic acids is also reported.

Beiler, Barbara; Sáfrány, Ágnes

2007-08-01

162

Development of adsorbent from Teflon waste by radiation induced grafting: equilibrium and kinetic adsorption of dyes.  

PubMed

Mutual radiation grafting technique was employed to graft polyacrylic acid (PAA) onto Polytetrafluoroethylene (Teflon) scrap using high energy gamma radiation. Polyacrylic acid-g-Teflon (PAA-g-Teflon) adsorbent was characterized by grafting extent measurement, FTIR spectroscopy, SEM and wet ability & surface energy analysis. The PAA-g-Teflon adsorbent was studied for dye adsorption from aqueous solution of basic dyes, namely, Basic red 29 (BR29) and Basic yellow 11 (BY11). The equilibrium adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models, whereas, adsorption kinetics was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. Equilibrium adsorption of BR29 was better explained by Langmuir adsorption model, while that of BY11 by Freundlich adsorption model. The adsorption capacity for BY11 was more than for BR29. Separation factor (R(L)) was found to be in the range 0 < R(L) < 1, indicating favorable adsorption of dyes. Higher coefficient of determination (r(2) > 0.99) and better agreement between the q(e,cal) and q(e,exp) values suggested that pseudo-second order kinetic model better represents the kinetic adsorption data. The non-linearity obtained for intra-particle diffusion plot indicated, more than one process is involved in the adsorption of basic dyes. The desorption studies showed that ~95% of the adsorbed dye could be eluted in suitable eluent. PMID:21855214

Goel, N K; Kumar, Virendra; Pahan, S; Bhardwaj, Y K; Sabharwal, S

2011-10-15

163

Revival of the R-group approach: a "CTA-shuttled" grafting from approach for well-defined cylindrical polymer brushes via RAFT polymerization.  

PubMed

The synthesis of well-defined cylindrical polymer brushes (CPBs) from a linear polymer backbone with a high density of RAFT functionalities ("grafting from" approach) is challenging when the chain transfer agent (CTA) is attached to the backbone via its R-group. It is proposed that the difficulties of the R-group approach in controlling the grafting polymerization are induced by the "entrapment" of active free radicals within individual growing CPBs. A facile "CTA-shuttled" R-group approach overcoming this entrapment effect is developed, and used to synthesize well-defined CPBs with polystyrene or poly(tert-butyl acrylate) branches and core-shell CPBs with polystyrene-block-poly(N-isopropylacrylamide) branches. The polydispersity index (PDI = 1.23) of the obtained CPBs with polystyrene branches is much lower than that from the conventional R-group approach (PDI = 2.18). Monte Carlo simulations confirm that the advantage of the "CTA-shuttled" R-group approach consists in the release of the active radicals from the trapping CPB systems. PMID:24115272

Zheng, Zhicheng; Ling, Jun; Müller, Axel H E

2014-01-01

164

Poly(2-hydroxyethyl methacrylate) grafted halloysite nanotubes as a molecular host matrix for luminescent ions prepared by surface-initiated RAFT polymerization and coordination chemistry  

NASA Astrophysics Data System (ADS)

A fluorescent nanohybrid complex comprising of halloysite nanotubes (HNTs), poly(2-hydroxyethyl methacrylate) (PHEMA), and europium ions (Eu3+) was synthesized by the combination of surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization and coordination chemistry. Initially, PHEMA was grafted from the HNTs by SI-RAFT and then reacted with succinic anhydride to provide carboxyl acid groups on the external layers of HNTs-g-PHEMA nanohybrids. The subsequent coordination of the nanohybrids with Eu3+ ions afforded photoluminescent Eu3+ tagged HNTs-g-PHEMA nanohybrid complexes (HNTs-g-PHEMA-Eu3+). The structure, morphology, and fluorescence properties of the Eu3+ coordinated nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR, XPS, and EDS analyses suggested the formation of the HNTs-g-PHEMA-Eu3+ nanohybrids. FE-SEM images indicated the immobilization of polymer layers on HNTs. TGA scans further demonstrated the grafting of PHEMA onto HNTs surface. The optical properties of HNTs-g-PHEMA-Eu3+ nanohybrid complexes were investigated by photoluminescence spectroscopy.

Islam, Md. Rafiqul; Bach, Long Giang; Lim, Kwon Taek

2013-07-01

165

Role of Polymeric Endosomolytic Agents in Gene Transfection: A Comparative Study of Poly(l-lysine) Grafted with Monomeric l-Histidine Analogue and Poly(l-histidine).  

PubMed

Endosomal entrapment is one of the main barriers that must be overcome for efficient gene expression along with cell internalization, DNA release, and nuclear import. Introducing pH-sensitive ionizable groups into the polycationic polymers to increase gene transfer efficiency has proven to be a useful method; however, a comparative study of introducing equal numbers of ionizable groups in both polymer and monomer forms, has not been reported. In this study, we prepared two types of histidine-grafted poly(l-lysine) (PLL), a stacking form of poly(l-histidine) (PLL-g-PHis) and a mono- l-histidine (PLL-g-mHis) with the same number of imidazole groups. These two types of histidine-grafted PLL, PLL-g-PHis and PLL-g-mHis, showed profound differences in hemolytic activity, cellular uptake, internalization, and transfection efficiency. Cy3-labeled PLL-g-PHis showed strong fluorescence in the nucleus after internalization, and high hemolytic activity upon pH changes was also observed from PLL-g-PHis. The arrangement of imidazole groups from PHis also provided higher gene expression than mHis due to its ability to escape the endosome. mHis or PHis grafting reduced the cytotoxicity of PLL and changed the rate of cellular uptake by changing the quantity of free ?-amines available for gene condensation. The subcellular localization of PLL-g-PHis/pDNA measured by YOYO1-pDNA intensity was highest inside the nucleus, while the lysotracker, which stains the acidic compartments was lowest among these polymers. Thus, the polymeric histidine arrangement demonstrate the ability to escape the endosome and trigger rapid release of polyplexes into the cytosol, resulting in a greater amount of pDNA available for translocation to the nucleus and enhanced gene expression. PMID:25144273

Hwang, Hee Sook; Hu, Jun; Na, Kun; Bae, You Han

2014-10-13

166

Fundamental investigation of ultraviolet radiation effects in polymeric film-forming materials  

NASA Technical Reports Server (NTRS)

A literature search from 1958 to present was conducted on the effect of ultraviolet radiation on polymeric materials, with particular emphasis on vacuum photolysis, mechanisms of degradation, and energy transfer phenomena. The literature from 1958 to 1968 was searched manually, while the literature from 1968 to present was searched by using a computerized keyword system. The primary objective was to provide the necessary background information for the design of new or modified materials with improved stability to the vacuum-radiation environment of space.

Giori, C.; Yamauchi, T.; Llewellen, P.; Gilligan, J.

1974-01-01

167

Radiation induced graft copolymerization of n-butyl acrylate onto poly(ethylene terephthalate) (PET) films and thermal properties of the obtained graft copolymer  

NASA Astrophysics Data System (ADS)

n-Butyl acrylate (BA) was successfully grafted onto poly(ethylene terephthalate) (PET) film using simultaneous radiation induced graft copolymerization with gamma rays. When BA concentration ranges from 20% to 30%, the Degree of Grafting (DG), measured by gravimetry and 1H NMR, increases with the monomer concentration and absorbed dose, but decreases with dose rate from 0.83 to 2.53 kGy/h. The maximum DG can reach up to 22.1%. The thermal transition temperatures such as glass-transition temperature ( Tg) and cold-crystallization temperature ( Tcc) of PET in grafted films were little different from those in original PET film, indicating that microphase separation occurred between PBA side chains and PET backbone. This work implied that if PET/elastomers (e.g., acrylate rubber) blends are radiated by high energy gamma rays under a certain condition, PET-g-polyacrylate copolymer may be produced in-situ, which will improve the compatibility between PET and the elastomers so as to improve the integral mechanical properties of PET based engineering plastic.

Ping, Xiang; Wang, Mozhen; Ge, Xuewu

2011-05-01

168

Cell culture on polymers prepared by radiation-induced polymerization of various glass-forming monomers.  

PubMed

The growth of cells on polymers prepared by the radiation polymerization of monomethacrylate and dimethacrylate was investigated. Cell growth was affected greatly by such properties of the polymers as water content, wettability, and porosity. Growth was promoted remarkably by rinsing the polymers with warm water at 60-70 degrees C and by irradiation of polymers with an electron beam. Cell growth decreased with increasing oxyethylene length (n) in the polymerized dimethacrylate of same series, CH2C(CH3)CO(OCH2CH2)nOCOC(CH3)CH2. A decrease in the hydrophilicity of the polymer increased cell growth rate. Formation of pore structures in the polymer films also increased the cell growth. PMID:6679189

Yoshii, F; Kaetsu, I

1983-04-01

169

Radiation-grafting of 2-hydroxyethylmethacrylate and oligo (ethylene glycol) methyl ether methacrylate onto polypropylene films by one step method  

NASA Astrophysics Data System (ADS)

Polypropylene films were modified with 2-hydroxyethylmethacrylate (HEMA) and oligo (ethylene glycol) methyl ether methacrylate (OEGMA) using the pre-irradiation method with gamma-rays (one step method). The effect of absorbed dose from 10 to 100 kGy, temperature (50, 60, and 70 °C), monomer concentration between 12.5% and 62.5%, monomers ratio from 10% to 90% and reaction time from 5 to 50 h; on the degree of grafting was determined. The grafted samples were analyzed by FTIR-ATR, TGA, DSC, swelling, and contact angle. Grafts onto polymeric films between 3% and 109% were obtained at doses from 10 to 100 kGy and a dose rate around 7.4 kGy/h. The graft percent increased with the content in HEMA in the HEMA:OEGMA feed mixture, which indicates a lower reactivity of OEGMA compared to HEMA. The hydrogel layer grafted on the polypropylene substrate increases the hydrophilicity of the surface and also provides certain temperature-responsiveness, which may be of interest for biomedical applications.

Ramírez-Jiménez, Alejandro; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2012-01-01

170

PDMS-Glass bonding using grafted polymeric adhesive - Alternative process flow for compatibility with patterned biological molecules  

PubMed Central

We report a novel modification of silicone elastomer, polydimethylsiloxane (PDMS) with a polymer graft that allows interfacial bonding between elastomer and glass substrate to be performed without exposure of said substrate to harsh treatment conditions like oxygen plasma. Organic molecules can thus be patterned within microfluidic channels and still remain functional post-bonding. In addition, after polymer grafting the PDMS can be stored in a desiccator for at least 40 days, and activated upon exposure to acidic buffer for bonding. The bonded devices remain fully bonded in excess of 80 psi driving pressure, with no signs of compromise to the bond integrity. Finally, we demonstrate the compatibility of our method with biological molecules using a proof-of-concept DNA sensing device, in which fluorescently-labelled DNA targets are successfully captured by a patterned probe in a device sealed using our method, while the pattern on a plasma-treated device was completely destroyed. Therefore, this method provides a much-needed alternative bonding process for incorporation of biological molecules in microfluidic devices. PMID:22858861

Beh, Cyrus Weijie; Zhou, Weizhuang

2013-01-01

171

Synthesis of palladium nanoparticles in a ceramic matrix using radiation grafting method  

NASA Astrophysics Data System (ADS)

Silicon carbide (SiC) ceramics containing palladium (Pd) nanoparticles were synthesized by the combination of the radiation grafting method, which allowed for uniform dispersion of Pd ions in polycarbosilane (PCS), and subsequent heat treatment, which was used to promote the bleedout phenomenon. The size and distribution of the Pd nanoparticles varied with the heat-treatment temperature. TEM and XRD analyses indicated that Pd nanoparticles of 2-5 nm in size were homogeneously distributed in the SiC ceramic matrix at temperatures lower than 1173 K. At a temperature of 1373 K, the size of these particles was found to increase and a portion of Pd was changed into Pd silicide. The Pd nanoparticles in samples heated at temperatures lower than 1173 K showed catalytic activity for hydrocarbon oxidation, whereas samples treated at 1373 K did not show any catalytic activity. These results suggest that Pd nanoparticles were formed on the SiC matrix at temperatures lower than 1173 K. The bleedout process enables the production of Pd nanoparticles as a combustion catalyst from radiation-grafted Pd-PCS.

Yoshimura, Kimio; Hakoda, Teruyuki; Sugimoto, Masaki; Yamamoto, Shunya; Yoshikawa, Masahito

2011-04-01

172

Study on slow release anti-cancer drugs prepared by radiation induced polymerization  

NASA Astrophysics Data System (ADS)

This paper reports the research results which the anticancer drugs Ara-C with controlled slow release were made by radiation induced polymerization of monomers such as methacrylates at room temperature. Our studies showed that not only hydrophilic synthetic polymers but also hydrophobic polymers such as hydrophobic methacrylates (including MMA, EMA, and BMA) could be used to the immobilization. In vitro the rate of drugs release was controlled by the many factors such as the content of drugs, the monomer material, the crosslinking agent, the irradiation dose and the water content, etc.

Huaijiang, Xie; Juzhong, Song; Tao, Peng

1993-10-01

173

Preparation of PTFE-based fuel cell membranes by combining latent track formation technology with graft polymerization  

NASA Astrophysics Data System (ADS)

Swift heavy 56 MeV 15N 3+ ions were generated with particle fluences of 0, 3×10 6, 3×10 7, 3×10 8, 3×10 9 ions/cm 2 to form a latent track zone in a 25-?m-thick film of polytetrafluoroethylene (iPTFE). Styrene (St) was then grafted onto the iPTFE films by UV-irradiation or pre-?-irradiation, and after sulfonation iPTFE-based proton-conducting membranes were obtained, here called, iPTFE-g(UV)-PStSA and iPTFE-g(?)-PStSA membranes, respectively, which had a straight cylindrical damage zone around the ion path. The degree of grafting was found to be about 7.5% with a particle fluence of 3×10 7 ions/cm 2 and with either the UV-method or the ?-method. The ion-exchange capacity, proton conductivity in the thickness direction, MeOH permeability, tensile strength and elongation at break of the obtained iPTFE-g(UV)-PStSA membrane were 0.50 mmol/g, 0.06 S/cm, 0.15×10 -6 cm 2/s, 50 MPa and 600%, in contrast to 0.06 mmol/g, 0.06 S/cm, 0.35×10 -6 cm 2/s, 19 MPa and 210% for the iPTFE-g(?)-PStSA membrane, respectively. In comparison, the Nafion 112 measured in our laboratory exhibited an ion-exchange capacity of 0.91 mmol/g, a proton conductivity of 0.06 S/cm, a MeOH permeability of 1.02×10 -6 cm 2/s, a tensile strength of 35 MPa and an elongation at break of 295%. It can be concluded from these data that the lower crossover of MeOH, the same proton conductibility, the lower ion-exchange capacity, and the superior mechanical properties of the UV-grafted proton-conducting membranes compared to the Nafion make them promising materials for widespread application in direct methanol fuel cells. On the other hand, the tests of mechanical strength showed that the PTFE base film is subject to degradation by the ion-beam irradiation as well as the ?-irradiation.

Yoshida, Masaru; Kimura, Yosuke; Chen, Jinhua; Asano, Masaharu; Maekawa, Yasunari

2009-12-01

174

Approach to cross-linked polynorbornene/ZnO nanocomposites through nitroxide-mediated free radical graft polymerization and in situ hydrolysis  

NASA Astrophysics Data System (ADS)

In this study, we reported an alternative strategy for fabricating stable cross-linked poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde)/ZnO (P(BN/NCA)/ZnO) nanocomposite films based on nitroxide-mediated free radical polymerization (NMRP) and in situ hydrolysis. Firstly, the macroinitiator poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde) alkoxyamine (P(BN/NCA)-TIPNO) was synthesized through the attachment of an alkoxyamine to polynorbornene derivative. And then the cross-linked graft copolymers poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde)-g-poly(zinc dimethacrylate) (P(BN/NCA)-g-PZDMA) were prepared using zinc dimethacrylate (ZDMA) and the as-prepared macroinitiator P(BN/NCA)-TIPNO by NMRP. Due to the two Cdbnd C bonds in each ZDMA molecule, the resulting cross-linked polymer connected the precursor of ZnO nanocrystals and polymer with covalent band, leading to a homogenous distribution of Zn2+ at the molecular level. Finally, ZnO nanocrystals were generated in situ by hydrolyzing the polymer film in NaOH aqueous solution. ZnO nanocrystals were homogeneously dispersed in the cross-linked polymer matrix without aggregation. Compared with the physical blending of non-cross-linked P(BN/NCA)/ZnO nanocomposite film, the cross-linked P(BN/NCA)/ZnO nanocomposite films exhibited good optical properties and photoluminescence (PL) stability owing to the function of cross-linked template.

Li, Fan; Zhang, Lin; Chen, Yiwang

2012-07-01

175

Electrolytic membrane formation of fluoroalkyl polymer using a UV-radiation-based grafting technique and sulfonation  

NASA Astrophysics Data System (ADS)

A sulfonated fluoroalkyl graft polymer (FGP) membrane was prepared as a polymer electrolyte. First, the FGP membrane was grafted with styrene under UV irradiation. The grafted FGP was then sulfonated to functionalize it for proton conductivity. The grafting degree of the membrane increased with increasing grafting time during UV irradiation. The proton conductivity of the membrane increased with increasing grafting degree. The swelling ratio was independent of the grafting time, however, the water uptake increased with increasing grafting degree. Based on these results, it was found that the UV-initiated styrene grafting occurred along the membrane thickness direction. Moreover, the membrane was embedded within the glass fibers of the composite. This composite electrolytic membrane had 1.15 times the proton conductivity of a Nafion 117 membrane.

Shironita, Sayoko; Mizoguchi, Satoko; Umeda, Minoru

2011-03-01

176

Gold-loaded polymeric micelles for computed tomography-guided radiation therapy treatment and radiosensitization.  

PubMed

Gold nanoparticles (AuNPs) have generated interest as both imaging and therapeutic agents. AuNPs are attractive for imaging applications since they are nontoxic and provide nearly three times greater X-ray attenuation per unit weight than iodine. As therapeutic agents, AuNPs can sensitize tumor cells to ionizing radiation. To create a nanoplatform that could simultaneously exhibit long circulation times, achieve appreciable tumor accumulation, generate computed tomography (CT) image contrast, and serve as a radiosensitizer, gold-loaded polymeric micelles (GPMs) were prepared. Specifically, 1.9 nm AuNPs were encapsulated within the hydrophobic core of micelles formed with the amphiphilic diblock copolymer poly(ethylene glycol)-b-poly(?-capralactone). GPMs were produced with low polydispersity and mean hydrodynamic diameters ranging from 25 to 150 nm. Following intravenous injection, GPMs provided blood pool contrast for up to 24 h and improved the delineation of tumor margins via CT. Thus, GPM-enhanced CT imaging was used to guide radiation therapy delivered via a small animal radiation research platform. In combination with the radiosensitizing capabilities of gold, tumor-bearing mice exhibited a 1.7-fold improvement in the median survival time, compared with mice receiving radiation alone. It is envisioned that translation of these capabilities to human cancer patients could guide and enhance the efficacy of radiation therapy. PMID:24377302

Al Zaki, Ajlan; Joh, Daniel; Cheng, Zhiliang; De Barros, André Luís Branco; Kao, Gary; Dorsey, Jay; Tsourkas, Andrew

2014-01-28

177

Gold-Loaded Polymeric Micelles for Computed Tomography-Guided Radiation Therapy Treatment and Radiosensitization  

PubMed Central

Gold nanoparticles (AuNPs) have generated interest as both imaging and therapeutic agents. AuNPs are attractive for imaging applications since they are nontoxic and provide nearly three times greater X-ray attenuation per unit weight than iodine. As therapeutic agents, AuNPs can sensitize tumor cells to ionizing radiation. To create a nanoplatform that could simultaneously exhibit long circulation times, achieve appreciable tumor accumulation, generate computed tomography (CT) image contrast, and serve as a radiosensitizer, gold-loaded polymeric micelles (GPMs) were prepared. Specifically, 1.9 nm AuNPs were encapsulated within the hydrophobic core of micelles formed with the amphiphilic diblock copolymer poly(ethylene glycol)-b-poly(?-capralactone). GPMs were produced with low polydispersity and mean hydrodynamic diameters ranging from 25 to 150 nm. Following intravenous injection, GPMs provided blood pool contrast for up to 24 h and improved the delineation of tumor margins via CT. Thus, GPM-enhanced CT imaging was used to guide radiation therapy delivered via a small animal radiation research platform. In combination with the radiosensitizing capabilities of gold, tumor-bearing mice exhibited a 1.7-fold improvement in the median survival time, compared with mice receiving radiation alone. It is envisioned that translation of these capabilities to human cancer patients could guide and enhance the efficacy of radiation therapy. PMID:24377302

2013-01-01

178

Radiation-induced grafting of styrene into poly(vinylidene fluoride) film by simultaneous method with two different solvents  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of styrene into poly(vinylidene fluoride) (PVDF) films with 0.125 mm thickness at doses of 1 and 2.5 kGy in the presence of a styrene/N,N-dimethylformamide (DMF) solution (1:1, v/v) and at doses of 20, 40 and 80 kGy in presence of a styrene/toluene solution (1:1, v/v) at dose rate of 5 kGy h-1 was carried out by the simultaneous method under nitrogen atmosphere and room temperature, using gamma rays from a Co-60. The films were characterized before and after modification by calculated grafting yield (GY %), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG). GY results shows that grafting increases with dose, and the grafting of styrene was confirm by FT-IR due to the new characteristic peaks and by the TG and DSC attributed to changes in thermal behavior of the grafted material. Results showed that the system allows the controlled grafting of styrene into PVDF using gamma rays at doses as low as 1 kGy in DMF.

Ferreira, H. P.; Parra, D. F.; Lugao, A. B.

2012-09-01

179

Kinetics and characterization of radiation-induced grafting of styrene on fluoropolymers  

NASA Astrophysics Data System (ADS)

Grafting of styrene solution onto poly(ethylene-co-tetrafluoroethylene) (ETFE) was carried out by the pre-irradiation method. ETFE films were irradiated by 1.5 MeV electron beams in air. The influence of grafting temperature (50 to 80°C) has been investigated. It was found that the saturation grafting yield and the initial rate follow an Arrhenius law. The volume grafting yields were measured by FTIR spectroscopy in transmission and by weighing and the 'surface' grafting yields by FTIR-ATR. The results showed that grafting reaction is not monomer diffusion controlled in 30 ?m film, nevertheless heterogeneities are revealed. By in-situ ESR, the decay of peroxy radicals was recorded under various heating and grafting conditions. These experiments suggest that the peroxy radicals react rapidly with monomer, but do not initiate the grafting process. The propagating radicals were not detectable, which may indicate that polystyrene chains are very long.

Guilmeau, I.; Esnouf, S.; Betz, N.; Le Moël, A.

1997-08-01

180

Study of radiation-grafted FEP-G-polystyrene membranes as polymer electrolytes in fuel cells  

Microsoft Academic Search

Proton exchange membranes for fuel cell applications were synthesized by pre-irradiation grafting of styrene\\/divinylbenzene mixtures into poly(fluoroethylene-co-hexafluoropropylene) films and subsequent sulfonation. Grafting of pre-existing films overcomes the problem of shaping the grafted polymer into thin membranes and makes this process a potentially cheap and easy technique for the preparation of solid polymer electrolytes.The grafted membranes were characterized by measuring their

Felix N. Büchi; Bhuvanesh Gupta; Otto Haas; Günther G. Scherer

1995-01-01

181

A study of ethanol production of yeast cells immobolized with polymer carrier produced by radiation polymerization  

NASA Astrophysics Data System (ADS)

Polymer carriers, poly(hydroxyethyl acrylate(HEA)-methoxy polyethylene glycol methylacrylate (M-23G)) and poly (hydroxyethyl accrylate(HEA)-glycidyl methlacrylate(GMA)) using for immobilization of yeast cells were prepared by radiation polymerization at low temperature. Yeast cells were immobilized through adhesion and multiplication of yeast cells themselves. The ethanol productivity of immobilized yeast cells with these carriers was related to the monomer composition of polymers and the optimum monomer composition was 20% : 10% in poly(HEA-M-23G) and 17%: 6% in poly(HEA-GMA). In this case, the ethanol productivity of immobilized yeast cells was 29mg/ml/h which was about 4 times that of cells in free system. The relationship between the activity of immobilized yeast cells and the water content of polymer carrier were also discussed.

Zhaoxin, Lu; Fujimura, Takashi

1993-10-01

182

Immobilization of antibodies and enzyme-labeled antibodies by radiation polymerization  

SciTech Connect

Immobilization of antibodies and enzyme-labeled antibodies by radiation polymerization at low temperatures was studied. The antibody activity of antibody was not affected by irradiation at an irradiation dose of below 8 MR and low temperatures. Immobilization of peroxidase-labeled anti-rabbit IgG goat IgG, anti-peroxidase, peroxidase, and anti-alpha-fetoprotein was carried out with hydrophilic and hydrophobic monomers. The activity of the immobilized enzyme-labeled antibody membranes varied with the thickness of the membranes and increased with decreasing membrane thickness. The activity of the immobilized antibody particles was varied by particle size. Immobilized anti-alpha-fetoprotein particles and membranes can be used for the assay of alpha-fetoprotein by the antigen-antibody reaction, such as a solid-phase sandwich method with high sensitivity.

Kumakura, M.; Kaetsu, I.; Suzuki, M.; Adachi, S.

1983-04-01

183

Microfiltration membranes prepared from polyethersulfone powder grafted with acrylic acid by simultaneous irradiation and their pH dependence  

NASA Astrophysics Data System (ADS)

Polyethersulfone (PES) powder was grafted with acrylic acid (AAc) by simultaneous ?-ray irradiation. The kinetics of the radiation induced graft polymerization was studied and the grafted PES powder was characterized. Then, microfiltration (MF) membranes were prepared from PES-g-PAAc powder with different degrees of grafting (DG) under phase inversion method. The swelling behavior and the mean pore size of MF membranes were measured, and the filtration property was tested. The results showed that the pore size and the flux of MF membranes increased with the increase in DG. And, MF membranes' properties were dependent on the pH value.

Deng, Bo; Li, Jingye; Hou, Zhengchi; Yao, Side; Shi, Liuqing; Liang, Guoming; Sheng, Kanglong

2008-07-01

184

Free-volume structure of fluoropolymer-based radiation-grafted electrolyte membranes investigated by positron annihilation lifetime spectroscopy  

NASA Astrophysics Data System (ADS)

In the field of polymer-electrolyte-membrane (PEM) fuel cell technology, the structures of free-volume holes in the PEMs are very important because they are correlated to the supplied-gas crossover phenomenon, which sometimes deteriorates the cell performance. In this study, we investigated the size and location of free-volume holes in the crosslinked-polytetrafluoroethylene (cPTFE) based radiation-grafted PEMs by positron annihilation lifetime (PAL) spectroscopy. For comparison, the base cPTFE and polystyrene grafted films were also measured. From the analysis of PAL spectra, it was found that there were free-volume holes with different radius of 0.28-0.30 nm and 0.44-0.45 nm. The smaller holes should be located in both PTFE crystallites and poly(styrene sulfonic acid) grafts, while the larger holes are considered to exist in amorphous PTFE phases.

Sawada, S.; Kawasuso, A.; Maekawa, M.; Yabuuchi, A.; Maekawa, Y.

2010-04-01

185

Measurements of the temperature dependence of radiation induced conductivity in polymeric dielectrics  

NASA Astrophysics Data System (ADS)

This study measures Radiation Induced Conductivity (RIC) in five insulating polymeric materials over temperatures ranging from ~110 K to ~350 K: polyimide (PI or Kapton HN(TM) and Kapton E(TM)), polytetraflouroethylene (PTFE or Teflon(TM)), ethylene-tetraflouroethylene (ETFE or Tefzel(TM)), and Low Density Polyethylene (LDPE). RIC occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. Conductivity was measured when a voltage was applied across vacuum-baked, thin film polymer samples in a parallel plate geometry. RIC was calculated as the difference in sample conductivity under no incident radiation and under an incident ~4 MeV electron beam at low incident dose rates of 0.01 rad/sec to 10 rad/sec. The steady-state RIC was found to agree well with the standard power law relation, sigmaRIC(D?) = kRIC(T) D?Delta(T) between conductivity, sigmaRIC and adsorbed dose rate, D?. Both the proportionality constant, kRIC, and the power, Delta, were found to be temperature-dependent above ~250 K, with behavior consistent with photoconductivity models developed for localized trap states in disordered semiconductors. Below ~250 K, kRIC and Delta exhibited little change in any of the materials.

Gillespie, Jodie

186

Synthesis of CO2/N2-Triggered Reversible Stability-Controllable Poly(2-(diethylamino)ethyl methacrylate)-grafted-AuNPs by Surface-Initiated Atom Transfer Radical Polymerization.  

PubMed

CO2/N2-triggered stability-controllable gold nanoparticles (AuNPs) grafted with poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) layers (PDEAEMA-g-AuNPs) were synthesized by the surface-initiated atom transfer radical polymerization of DEAEMA with AuNPs bearing the bis[2-(2-bromoisobutyryloxy)undecyl] layer (grafting from method). Extension of the PDEAEMA chain length increased the stability of the PDEAEMA-g-AuNPs in CO2-bubbled water because of the electrosteric repulsion of the protonated PDEAEMA layer. The chain-length-dependent stability of PDEAEMA-g-AuNPs was confirmed by DLS and UV-vis spectra by using the localized surface plasmon resonance property of the AuNPs, where the extinction wavelength was shifted toward shorter wavelength with increasing PDEAEMA chain length. The reversible stability change with the gas stimuli of CO2/N2 was also successfully demonstrated. Finally, the transfer across the immiscible interface between water and organic solvent was successfully demonstrated by N2-triggered insolubilization of PDEAEMA layer on AuNPs in the aqueous phase, leading to the successful collection of AuNPs using organic solvent from the aqueous phase. Our "grafting from" method of reversible stability-controllable AuNPs can be applied to develop advanced materials such as reusable optical AuNP-based nanosensors because the molecular recognition layer can be constructed by two-step polymerization. PMID:25268967

Kitayama, Yukiya; Takeuchi, Toshifumi

2014-10-28

187

Application of radiation grafted media for lectin affinity separation and urease immobilization: A novel approach to tumor therapy and renal disease diagnosis  

NASA Astrophysics Data System (ADS)

Carriers modified by synergistic radiation grafting are used as affinity media for the separation of a lectin from a mistletoe extract. The grafted supports show distinctly superior properties when compared to conventional affinity media. The application of these carriers as urease immobilization support incorporated in a conductimetric bioreactor for urea analysis as potential diagnostic device in renal diseases is also described.

Müller-Schulte, D.; Daschek, W.

1995-09-01

188

Radiation damage in patients treated by total-body irradiation, bone marrow grafting, and cyclosporin  

SciTech Connect

The bone marrow (BM) and peripheral blood (PB) from 63 patients were assessed for the presence of chromosomal aberrations after bone marrow transplantation (BMT) following total body irradiation (TBI) for leukemia. Forty-one patients showed no abnormalities in either BM or PB, and 22 had aberrations in either BM or PB or both. Only stable aberrations were found in the BM, but both stable and unstable abnormalities were present in the PB, the majority showing only unstable aberrations. Among the 25 patients who had a leukemic relapse, clonal chromosomal abnormalities were found in the BM of 12 out of the 16 cases for whom marrow was studied at the time of the relapse. A statistically significant negative correlation between leukemic relapse and graft versus host disease (GvHD) was found, but the relationships between chromosome damage and leukemic relapse, GvHD, and the pretransplant radiation dose and between the radiation dose and both leukemic relapse and GvHD were not significant.

Baker, M.C.; Lawler, S.D.; Harris, H.; Barrett, A.; Powles, R.L.

1986-03-01

189

Effects of ?-ray radiation grafting on aramid fibers and its composites  

NASA Astrophysics Data System (ADS)

Armos fiber was modified by Co 60 ?-ray radiation in the different concentrations' mixtures of phenol-formaldehyde and ethanol. Interlaminar shear strength (ILSS) was examined to characterize the effects of the treatment upon the interfacial bonding properties of Armos fibers/epoxy resin composites. The results showed that the ILSS of the composite, whose fibers were treated by 500 kGy radiation in 1.5 wt% PF, was improved by 25.4%. Nanoindentation technique analysis showed that the nanohardnesses of the various phases (the fiber, the interface and the matrix) in the composite, whose fibers were treated, were correspondingly higher than those in the composite, whose fibers were untreated. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectrum confirmed the increase in the polar groups at the fibers' surface. Atomic force microscopy (AFM) results revealed that the surface of the fibers treated was rougher than that of the fibers untreated. The wettability of the fibers' surface was also enhanced by the treatment. The conclusion that ?-ray irradiation grafting significantly improved the surface properties of Armos fibers could be drawn.

Zhang, Y. H.; Huang, Y. D.; Liu, L.; Cai, K. L.

2008-03-01

190

Proton exchange membranes prepared by radiation-induced graft copolymerization from binary monomer mixtures onto poly(tetrafluoroethylene-co-hexafluoropropylene) film  

NASA Astrophysics Data System (ADS)

Sulfonic acid proton exchange membranes based on a poly(tetrafluoroethylene-co-hexafluoropropylene) film were synthesized through the single-step graft copolymerization of sodium styrenesulfonate and acrylic acid monomers from binary monomer aqueous solutions using the electron beam pre-irradiation method in air. The effects of the various polymerization parameters (absorbed dose, reaction time, and monomer ratio) on the degree of grafting were studied. A correlation between the degree of grafting and some of the physical-chemical properties (water uptake and ion-exchange capacity) of the synthesized copolymers was established. The distribution of the sulfonic acid groups was investigated across the thickness of several membranes in order to gain a better understanding of the graft copolymerization process from binary monomer aqueous solutions onto the fluorinated film and to synthesize membranes with optimal physical-chemical properties.

Cho, Hyun Kug; Bondar, Iuliia; Han, Do Hung; Kwon, Yong Kil

2010-05-01

191

Preparation and characterization of glycidyl methacrylate grafted 4-amino-1,2,4-triazole modified nonwoven fiber adsorbent for environmental application  

NASA Astrophysics Data System (ADS)

A novel 4-amino-1,2,4-triazole (ATZ) containing nonwoven fiber was prepared by means of radiation induced graft polymerization. For this purpose, glycidyl methacrylate (GMA) was grafted onto polyethylene coated polypropylene nonwoven fibers (NWF) in emulsion medium by using radiation induced graft polymerization. Grafting conditions were optimized and epoxy groups of grafted GMA were then modified with ATZ. Optimum conditions for modification were conducted in different solvents i.e. water and dioxane/water mixture at different amino triazole concentrations (5%, 10%, 20% (w/w)). Maximum modification was obtained in 10% (w/w) ATZ solution in dioxane/water mixture as a solvent at 80 °C. Prepared nonwoven fibers were characterized by FTIR and thermal analysis techniques.

Kavakl?, Cengiz; Akka? Kavakl?, P?nar; Güven, Olgun

2014-01-01

192

Pre-irradiation-induced graft reaction of maleic anhydride onto polypropylene  

NASA Astrophysics Data System (ADS)

The radiation induced graft polymerization is a well-known method to obtain new materials. Until recently, only conventional radiation sources, such as Co-60 and electron beams, were used. Moreover, part of the damage induced in polymers by heavy ions can produce active sites (peroxides and hydroperoxides) that are useful to initiate grafting reactions. Maleic anhydride (MAH) was grafted onto polypropylene (PP) wax with a number-average molecular weight (Mn) of 8000 by gamma pre-irradiation technique. Effects of total dose, monomer concentration, reaction time, and temperature on percentage of grafting are studied in detail. It is shown that the optimum conditions for grafting are temperature of 70 degrees C and total dose of 14.4 kGy. PP-g-MAH is characterized by infrared spectrum. Differential scanning calorimetry shows that the compatibility of PP-g-MAH is better than that of PP.

Tan, X. M.; Xu, Y. S.; Wang, C. L.

2006-09-01

193

Study of nitrile-containing proton exchange membranes prepared by radiation grafting: Performance and degradation in the polymer electrolyte fuel cell  

NASA Astrophysics Data System (ADS)

The fuel cell performance and durability of three kinds of styrene based radiation grafted membranes are investigated and compared in the single cell. The styrene/methacrylonitrile (MAN) co-grafted membrane exhibits the best performance among the tested radiation grafted membranes. The accelerated tests under open circuit voltage (OCV) conditions and post-mortem analysis demonstrate that the nitrile-containing membranes exhibit significantly enhanced durability compared to the pure styrene grafted membrane, which is associated with the reduced gas crossover rates and attributed to the improved gases barrier properties due to the polarity of the nitrile group. To understand the influence of each functional group in the co-monomer units, both styrene/MAN and styrene/acrylonitrile (AN) co-grafted membranes are evaluated in a set of tests at OCV. The degrees of loss of the graft components are subsequently quantitatively analyzed based on FTIR spectra, showing a comparable decomposition rate of grafted styrene units, but more loss of nitrile in case of the styrene/AN co-grafted membrane. The styrene/AN co-grafted membrane, with AN lacking protection at the ?-position in contrast to MAN, is found to be susceptible to significant hydrolysis, directly leading to an accelerated degradation in the late stages of the 130 h OCV test and inhomogeneous in-plane degradation.

Zhang, Zhuoxiang; Jetsrisuparb, Kaewta; Wokaun, Alexander; Gubler, Lorenz

2013-12-01

194

Swelling, ion uptake and biodegradation studies of PE film modified through radiation induced graft copolymerization  

NASA Astrophysics Data System (ADS)

An attempt to develop biodegradable polyethylene film grafting of mixture of hydrophilic monomers methacrylic acid (MAAc) and acrylamide (AAm) onto PE film has been carried out by preirradiation method using benzoyl peroxide as the radical initiator. Since ether linkages are susceptible to easy cleavage during degradation process, PE film was irradiated before the grafting reactions by ?-rays to introduce peroxidic linkages (PE-OO-PE) that offer sites for grafting. The effect of irradiation dose, monomer concentration, initiator concentration, temperature, time and amount of water on the grafting percent was determined. Maximum percentage of grafting of binary mixture (MAAc+AAm), (1792%) was obtained at a total concentration of binary monomer mixture=204.6×10 -2 mol/L ([MAAc]=176.5×10 -2 mol/L, [AAm]=28.1×10 -2 mol/L), [BPO]=8.3×10 -2 mol/L at 100 °C in 70 min. The grafted PE film was characterized by the Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopic (SEM) methods. Some selective properties of grafted films such as swelling studies, ion uptake and biodegradation studies have been investigated. The grafted films show good swelling in water, ion uptake studies shows promising results for desalination of brackish water and the soil burial test shows that PE film grafted with binary monomer mixture degrades up to 47% within 50 days.

Kaur, Inderjeet; Gupta, Nitika; Kumari, Vandna

2011-09-01

195

Cross-linked, ETFE-derived and radiation grafted membranes for anion exchange membrane fuel cell applications  

Microsoft Academic Search

To develop a series of cross-linked anion exchange membranes for application in fuel cells, poly(ethylene-co-tetrafluoroethylene) (ETFE) films was radiation grafted with vinyl benzyl chloride (VBC), followed by quaternization and crosslinking with 1,4-Diazabicyclo[2,2,2]octane (DABCO), alkylation with p-Xylylenedichloride (DCX), and quaternization again with trimethylamine (TMA). These anion exchange membranes were characterized in terms of water uptake, ion-exchange capacity, ionic conductivity as well

Jun Fang; Yi-xu Yang; Xiao-huan Lu; Mei-ling Ye; Wei Li; Yan-mei Zhang

196

Radiation-Induced Graft Copolymerization of Metacrylic Acid and Butyl Methacrylate onto Poly(3-hydroxybutyrate)  

Microsoft Academic Search

Poly(3-hydroxybutyrate) (PHB) is a biocompatible and biodegradable thermoplastic polyester obtained microbiologically. Its main drawbacks are its thermal instability, brittleness, and moderate hydrophobicity, which limit its applications. The present study involves the chemical modification of PHB by means of the synthesis and characterization of graft copolymers with two selected monomers. Typical monomers, methacrylic acid (MA) and butyl methacrylate (BuM), were graft

Maykel González; Manuel Rapado; Arllene Perez Gonzalez; Manuel González Pérez

2009-01-01

197

Technological aspects of planar structurizing on woven and knitted fabrics by localized radiation induced grafting  

NASA Astrophysics Data System (ADS)

One technological variant of radiationchemical grafting at selected areas of textile fabrics are shown for the system polyamide-acrylamide. The variant includes the treatment of selected areas with higher temperatures after homogeneous irradiation of the planar fabric. The local grafting leads to a structurizing and a larger moisture-sorption capability as well as additional dyeing pattern.

Raetzsch, M.; Paessler, H.; Heger, A.

198

Optimization strategies for radiation induced grafting of 4-vinylpyridine onto poly(ethylene-co-tetraflouroethene) film using Box-Behnken design  

NASA Astrophysics Data System (ADS)

The radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(ethylene-co-tetrafluoroethene) (ETFE) was optimized using the Box-Behnken factorial design available in the response surface method (RSM). The optimized grafting parameters; absorbed dose, monomer concentration, grafting time and reaction temperature were varied in four levels to quantify their effect on the grafting yield (GY). The validity of the statistical model was supported by the small deviation between the predicted (GY=61%) and experimental (GY=57%) values. The optimum conditions for enhancing GY were determined at the following values: monomer concentration of 48 vol%, absorbed dose of 64 kGy, reaction time of 4 h and temperature of 68 °C. A comparison was made between the optimization model developed for the present grafting system and that for grafting of 1-vinylimidazole (1-VIm) onto ETFE to confirm the validly and reliability of the Box-Behnken for the optimization of various radiation induced grafting reactions. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to investigate the properties of the obtained films and provide evidence for grafting.

Mahmoud Nasef, Mohamed; Shamsaei, Ezzatollah; Ghassemi, Payman; Ahmed Aly, Amgad; Hamid Yahaya, Abdul

2012-04-01

199

Determining the molecular origin of radiation damage/enhancement in electro-optic polymeric materials through polarized light microscopy  

NASA Astrophysics Data System (ADS)

Previous studies on the radiation effects upon polymer and polymer-based photonic materials suggest that the radiation resistance of the material is heavily dependent on the choice of polymer-host and guest-chromophore. The best results to date have been achieved with electro optic polymeric materials based on CLD1 doped in APC, which has resulted in improved performance at the device level upon gamma-ray irradiation at moderate doses. Still, our understanding of the physical mechanisms behind the enhancement of the performance is unclear. In this paper, we discuss how polarized light microscopy could be used as a means to quantify the effect of the different physical parameters that influence the optical response of electro-optic polymeric thin film samples.

Perez-Moreno, Javier

2014-09-01

200

SYNTHESIS OF STYRENE-METHYL METHACRYLATE NONRANDOM COPOLYMERS IN EMULSION SYSTEMS WITH COBALT60 GAMMA RADIATION  

Microsoft Academic Search

Graft copolymers were prepared by the irradation of polymer lattices ; swollen with monomer. The lattices used were prepared by radiation ; polymerization of emulsions to avoid the presence of initiator molecules in the ; second stage. Lattices of polystyrene swollen with methyl methacrylate and ; polymethyl methacrylate swollen with styrene were used. Polymerizations were ; followed dilatometrically and the

G. J. K. Acres; F. L. Dalton

1963-01-01

201

Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films  

NASA Astrophysics Data System (ADS)

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m2 day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1-5 kGy) and it was revealed that PS values were reduced significantly (p?0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1-1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1-5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p?0.05) with the rise of radiation dose.

Khan, Avik; Huq, Tanzina; Khan, Ruhul A.; Dussault, Dominic; Salmieri, Stephane; Lacroix, Monique

2012-08-01

202

Polymeric Materials With Additives for Durability and Radiation Shielding in Space  

NASA Technical Reports Server (NTRS)

Polymeric materials are attractive for use in space structures because of their light weight and high strength In addition, polymers are made of elements with low atomic numbers (Z), primarily carbon (C), hydrogen (H), oxygen (0), and nitrogen (N) which provide the best shielding from galactic cosmic rays (GCR) (ref. 1). Galactic cosmic rays are composed primarily of nuclei (i.e., fully ionized atoms) plus a contribution of about 2% from electrons and positrons. There is a small but significant component of GCR particles with high charge (Z > 10) and high energy (E >100 GeV) (ref. 2). These so-called HZE particles comprise only 1 to 2% of the cosmic ray fluence but they interact with very high specific ionization and contribute 50% of the long- term dose to humans. The best shield for this radiation would be liquid hydrogen, which is not feasible. For this reason, hydrogen-containing polymers make the most effective practical shields. Moreover, neutrons are formed in the interactions of GCR particles with materials. Neutrons can only lose energy by collisions or reactions with a nucleus since they are uncharged. This is a process that is much less probable than the Coulombic interactions of charged particles. Thus, neutrons migrate far from the site of the reaction in which they were formed. This increases the probability of neutrons reaching humans or electronic equipment. Fast neutrons (> 1 MeV) can interact with silicon chips in electronic equipment resulting in the production of recoil ions which can cause single event upsets (SEU) in sensitive components (ref. 3). Neutrons lose energy most effectively by elastic collisions with light atoms, particularly hydrogen atoms. Therefore, hydrogen-containing polymers are not only effective in interacting with GCR particles; they are also effective in reducing the energy of the neutrons formed in the interactions.

Kiefer, Richard

2011-01-01

203

Adsorption of Cr(VI) using cellulose microsphere-based adsorbent prepared by radiation-induced grafting  

NASA Astrophysics Data System (ADS)

Cellulose microsphere (CMS) adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto CMS followed by a protonation process. The FTIR spectra analysis proved that PDMAEMA was grafted successfully onto CMS. The adsorption of Cr(VI) onto the resulting adsorbent was very fast, the equilibrium adsorption could be achieved within 15 min. The adsorption capacity strongly depended on the pH of the solution, which was attributed to the change of both the existed forms of Cr(VI) and the tertiary-ammonium group of PDMAEMA grafted CMS with the pH. A maximum Cr(VI) uptake (ca. 78 mg g-1) was obtained as the pH was in the range of 3.0-6.0. However, even in strong acid media (pH 1.3), the adsorbents still showed a Cr(VI) uptake of 30 mg g-1. The adsorption behavior of the resultant absorbent could be described with the Langmuir mode. This adsorbent has potential application for removing heavy metal ion pollutants (e.g. Cr(VI)) from wastewater.

Li, Cancan; Zhang, Youwei; Peng, Jing; Wu, Hao; Li, Jiuqiang; Zhai, Maolin

2012-08-01

204

Effect of carbon-black treatment by radiation emulsion polymerization on temperature dependence of resistivity of carbon-black-filled polymer blends  

NASA Astrophysics Data System (ADS)

High dispersibility and stability of carbon black particles in low-density-polyethylene (LDPE) matrix were obtained by radiation emulsion polymerization on carbon particles surface, and electrical resistivities of its simple were examined. First carbon particles treatment on radiation emulsion polymerization on surface were synthesized by the reaction with a polymer-emulsion systems containing reactive group in the molecular unit, carbon particles and emulsifier. Then, the carbon particles treatment on radiation emulsion polymerization on surface was dispersed into LDPE, and its composites were prepared for electrical measurements. The effect of radiation crosslinking of the composite on the Positive temperature coefficient (PTC) and negative temperature coefficient (NTC) phenomenon was investigated. The experimental results showed that PTC and NTC effects of the composites were obviously influenced by the irradiation dose. Various microstructure-exploring means were used to study the conductive composite, such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM).

Shaojin, Jia; Pingkai, Jiang; Zhicheng, Zhang; Zhongguang, Wang

2006-04-01

205

Evaluation of Thermal Control Coatings and Polymeric Materials Exposed to Ground Simulated Atomic Oxygen and Vacuum Ultraviolet Radiation  

NASA Technical Reports Server (NTRS)

Numerous thermal control and polymeric samples with potential International Space Station applications were evaluated for atomic oxygen and vacuum ultraviolet radiation effects in the Princeton Plasma Physics Laboratory 5 eV Neutral Atomic Oxygen Facility and in the MSFC Atomic Oxygen Drift Tube System. Included in this study were samples of various anodized aluminum samples, ceramic paints, polymeric materials, and beta cloth, a Teflon-impregnated fiberglass cloth. Aluminum anodizations tested were black duranodic, chromic acid anodize, and sulfuric acid anodize. Paint samples consisted of an inorganic glassy black paint and Z-93 white paint made with the original PS7 binder and the new K2130 binder. Polymeric samples evaluated included bulk Halar, bulk PEEK, and silverized FEP Teflon. Aluminized and nonaluminized Chemfab 250 beta cloth were also exposed. Samples were evaluated for changes in mass, thickness, solar absorptance, and infrared emittance. In addition to material effects, an investigation was made comparing diffuse reflectance/solar absorptance measurements made using a Beckman DK2 spectroreflectometer and like measurements made using an AZ Technology-developed laboratory portable spectroreflectometer.

Kamenetzky, R. R.; Vaughn, J. A.; Finckenor, M. M.; Linton, R. C.

1995-01-01

206

Adsorption of uranium ions by resins with amidoxime and amidoxime/carboxyl group prepared by radiation-induced polymerization  

NASA Astrophysics Data System (ADS)

In order to recover uranium ions from seawater, chelate-type resins with amidoxime and amidoxime/carboxylic acid groups were prepared by radiation-induced polymerization of acrylonitrile (AN) and AN/acrylic acid and by subsequent amidoximation of cyano group of poly(AN), respectively. The resins were characterized by FT-IR, FT-Raman, solid-state 13C-NMR, SEM, and elemental analysis, respectively. The adsorption rate of uranium ion by resins with the amidoxime/carboxylic acid group were higher than that of resins with the amidoxime group. The adsorption of uranium ions in artificial seawater to chelate-type resins was also examined.

Choi, Seong-Ho; Choi, Min-Seok; Park, Yong-Tae; Lee, Kwang-Pill; Kang, Hee-Dong

2003-06-01

207

Radiation grafting of pH and thermosensitive N-isopropylacrylamide and acrylic acid onto PTFE films by two-steps process  

NASA Astrophysics Data System (ADS)

Polytetrafluoroethylene (PTFE) was grafted (g) with acrylic acid (AAc) by ?-ray pre-irradiation method to get PTFE-g-AAc films, then N-isopropylacrylamide (NIPAAm) was grafted onto PTFE-g-AAc films with ?-ray to get (PTFE-g-AAc)-g-NIPAAm. PTFE films were irradiated in air at a dose rate of 3.0 kGy h -1 and different radiation dose. The irradiated films were placed in glass ampoules, which contained aqueous solutions with different monomer concentration (AAc), and then they were heated at different temperatures and reaction time. NIPAAm onto PTFE-g-AAc was carried out with the same procedure with monomer concentration of 1 mol L -1. The thermosensitivity of the samples was defined and calculated as the ratio of the grafted samples swelling at 28 and 35 °C, and pH sensitivity defined as the ratio of the grafted samples swelling at pH 2 and 8.

Bucio, E.; Burillo, G.

2007-11-01

208

Synthesis of high-molecular-weight polymer of methyl chloride salt of N,N-dimethylaminoethyl methacrylate by radiation-induced polymerization at high pressure. [Gamma radiation  

SciTech Connect

Polymer of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate and its copolymer with acrylamide are used as cationic flocculants for the treatment of waste water containing organic suspensions. As reported, radiation-induced polymerization is one of the most convenient methods because of its temperature independence of initiation and extremely large G-value. In general, a flocculant with higher molecular weight has larger flocculation effects. The high-molecular-weight products were prepared in high monomer concentration and a low dose rate. This paper concerns the polymerization and copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate at high pressure, up to 7000 kg/cm/sup 2/, providing high-molecular-weight cationic flocculants.

Ishigaki, I.; Okada, T.; Sasuga, T.; Takehisa, M.; Machi, S.

1981-02-01

209

Fire proofing by radiation grafting (application on polyester and polypropylene). Scientific technical report  

SciTech Connect

This report outlines efforts to try out a modern technique, radition grafting, rather than chemical and heat fixation, to make textiles more fire-proof by reducing as much as possible the deterioration in conventional properties, in particular softness and handle, to which the former give rise. The expected consequences are twofold: possession of a general method for fire-proofing textile materials which retain the conventional initial characteristics more fully, and improvement of the durability of the fire-proof properties.

Hill, B.J.; Einsele, U.; Di Modica, G.; Wattiez, D.

1980-01-01

210

Development of novel hydrogels by modification of sterculia gum through radiation cross-linking polymerization for use in drug delivery  

NASA Astrophysics Data System (ADS)

In order to modify the sterculia gum polysaccharide, to develop the hydrogels meant for the drug delivery, we have prepared sterculia gum, 2-hydroxyethylmethacrylate (HEMA) and acrylic acid (AAc) based hydrogels by radiation-induced crosslinking polymerization. Polymeric networks (hydrogels) thus formed were characterized with SEMs, FTIR,TGA and swelling studies which were carried out as a function monomers concentration, radiation dose, amount of sterculia contents in the polymer matrix and nature of the swelling medium. This paper discusses the swelling kinetics of the hydrogels and release dynamics of anti-diarrhea model drug ornidazole from the hydrogels to evaluation of swelling and drug release mechanism. Diffusion exponent ' n' have 0.73, 0.56 and 0.61 values and gel characteristic constant ' k' have 1.28 × 10 -2, 2.95 × 10 -2 and 2.14 × 10 -2 values in distilled water, pH 2.2 buffer and pH 7.4 buffer. The release of drug from the polymer matrix occurred through non-Fickian diffusion mechanism. The values for the late time diffusion coefficients have been lower than the values of initial and average diffusion coefficients. It reflects that in the initial stages rate of release of drug from polymer matrix was higher as compared to the late stages, it means after certain time the drug release occurred in controlled manner.

Singh, Baljit; Vashishtha, Manu

2008-05-01

211

Influence of Mercerization Along with Ultraviolet (UV) and Gamma Radiation on Physical and Mechanical Properties of Jute Yarn by Grafting with 3?(Trimethoxysilyl) Propylmethacrylate (Silane) and Acrylamide Under UV Radiation  

Microsoft Academic Search

Jute yarns were pretreated by alkali (5% NaOH) and were grafted with two types of monomer such as 3?(trimethoxysilyl)?propylmethacrylate (silane) and acrylamide (AA) under ultraviolet (UV) radiation. The monomer concentrations were 30% in Methanol (MeOH) and irradiation times were 30 min and 60 min for silane and AA, respectively. The alkali?treated silane?grafted jute yarn produced enhanced tensile strength (TS) (265%), elongation at

M. Masudul Hassan; M. Rabiul Islam; S. Shehrzade; Mubarak A. Khan

2003-01-01

212

UV radiation-induced surface modulation time evolution in polymeric materials  

NASA Astrophysics Data System (ADS)

The reorganization processes at submicron level of the polymeric materials have been investigated because of their applications in optoelectronics and bio-science. We have obtained surface relief modulation in single step processing on the photo resist and polysiloxane films. But for technical applications the time evolution and stability of the induced surface structure is an important parameter and is a problem to be discussed. In case of single step surface relief formation on polymeric materials the process is connected with the photochromic behavior of the materials. As it is known the UV light induced effects on the material structure are reversible under the action of visible light, but with different speeds. In this report is analyzed the time evolution of the surface modulation obtained under the action of the UV light for azopolymers with different structures.

Apostol, I.; Apostol, D.; Damian, V.; Iordache, I.; Hurduc, N.; Sava, I.; Sacarescu, L.; Stoica, I.

2009-05-01

213

Kinetic study on the radiation-induced polymerization of HDDA and HDDMA  

NASA Astrophysics Data System (ADS)

The kinetics of the first steps of electrom beam (EB) initiated polymerization in cyclohexane solutions of hexanediol diacrylate (HDDA) and hexanediol dimethacrylate (HDDMA) were investigated by pulse radiolysis with transient spectroscopic detection. The maxima of the transient UV absorption spectra attributed to ?-carboxyalkyl radical in HDDA solution were shifted to longer wavelength by increasing monomer concentration from 1 mmol dm -3 to 50 mmol dm -3, indicating the onset of oligomer radical formation. In HDDMA solutions the shape of the transient spectra did not change significantly as a result of the lower reactivity of this monomer. The rate parameters of termination (2 kt) were determined for both monomers at different concentrations.

Takács, E.; Wojnárovits, L.

1997-08-01

214

Development of high-productivity, strong cation-exchange adsorbers for protein capture by graft polymerization from membranes with different pore sizes  

PubMed Central

This paper describes the surface modification of macroporous membranes using ATRP (atom transfer radical polymerization) to create cation-exchange adsorbers with high protein binding capacity at high product throughput. The work is motivated by the need for a more economical and rapid capture step in downstream processing of protein therapeutics. Membranes with three reported nominal pore sizes (0.2, 0.45, 1.0 ?m) were modified with poly(3-sulfopropyl methacrylate, potassium salt) tentacles, to create a high density of protein binding sites. A special formulation was used in which the monomer was protected by a crown ether to enable surface-initiated ATRP of this cationic polyelectrolyte. Success with modification was supported by chemical analysis using Fourier-transform infrared spectroscopy and indirectly by measurement of pure water flux as a function of polymerization time. Uniformity of modification within the membranes was visualized with confocal laser scanning microscopy. Static and dynamic binding capacities were measured using lysozyme protein to allow comparisons with reported performance data for commercial cation-exchange materials. Dynamic binding capacities were measured for flow rates ranging from 13 to 109 column volumes (CV)/min. Results show that this unique ATRP formulation can be used to fabricate cation-exchange membrane adsorbers with dynamic binding capacities as high as 70 mg/mL at a throughput of 100 CV/min and unprecedented productivity of 300 mg/mL/min. PMID:23175597

Chenette, Heather C.S.; Robinson, Julie R.; Hobley, Eboni; Husson, Scott M.

2012-01-01

215

Grafting of norfloxacin imprinted polymeric membranes on silica surface for the selective solid-phase extraction of fluoroquinolones in fish samples.  

PubMed

A high-density imprinted polymeric membrane was immobilized on a porous silica-gel support by polymerization of methacrylic acid with vinyl-silanized silica gel for the selective solid-phase extraction (SPE) of norfloxacin (NOR) in fish samples. The imprinted membranes showed high adsorption capacity (423.2 ?mol g(-1)), significant selectivity (k=14.64, k'=9.61) and good site accessibility (2h) for NOR. The conditions of SPE were investigated, and water (pH=6), methanol:water (1:1, v/v) and methanol-acetic acid-trifluoroacetic acid (90:9:1, v/v) were selected as the sample solvent, the washing solution and the eluting solution, respectively. Under the optimal SPE condition, three fluoroquinolone residues in fish were separated and detected by an off-line MIP-SPE-HPLC with better clean up and enrichment. The recoveries of norfloxacin, ofloxacin and ciprofloxacin were 89.3-94.8%, 69.3-102.8% and 85-90.5%, respectively, with relative standard deviations lower than 6.5%. The limits of detection (LOD) of the proposed method (S/N=3) were in a range of 2.65-3.65 ?g kg(-1), and the limits of quantification (LOQ, S/N=10) were in a range of 8.82-12.16 ?g kg(-1). PMID:22284491

Lv, Yun-Kai; Ma, Yong; Zhao, Xiao-Bo; Jia, Cui-Ling; Sun, Han-Wen

2012-01-30

216

Dyeing, moisture regain and mechanical properties of wool fabric grafted with PMMA by chemical and radiation-initiated methods  

NASA Astrophysics Data System (ADS)

PMMA polymer has been grafted onto wool fabric by two methods of grafting preirradiation method and chemical initiation using KMnO 4/H 2SO 4 system. The grafted wool showed an enhancement in dyeability towards some basic dyes differing in size and chemical structure. Preirradiated grafted wool exhibited a relatively higher dyeing affinity than that prepared by the chemical method. Graft yield of up to 26% of PPMA did not have a noticeable effect on the moisture regain of wool fabric. Further increase in graft yield was found to cause a slight reduction in moisture regain. The tensile strength was reduced by the graft process, but elongation at break was not affected.

El Naggar, A. M.; Marie, M. M.; El Gendy, E. H.; El Miligy, A. A.

1996-04-01

217

Optimization of reaction parameters of radiation induced grafting of 1-vinylimidazole onto poly(ethylene-co-tetraflouroethene) using response surface method  

NASA Astrophysics Data System (ADS)

Radiation induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetraflouroethene) (ETFE) was investigated. The grafting parameters such as absorbed dose, monomer concentration, grafting time and temperature were optimized using response surface method (RSM). The Box-Behnken module available in the design expert software was used to investigate the effect of reaction conditions (independent parameters) varied in four levels on the degree of grafting ( G%) (response parameter). The model yielded a polynomial equation that relates the linear, quadratic and interaction effects of the independent parameters to the response parameter. The analysis of variance (ANOVA) was used to evaluate the results of the model and detect the significant values for the independent parameters. The optimum parameters to achieve a maximum G% were found to be monomer concentration of 55 vol%, absorbed dose of 100 kGy, time in the range of 14-20 h and a temperature of 61 °C. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to investigate the properties of the obtained films and provide evidence for grafting.

Nasef, Mohamed Mahmoud; Aly, Amgad Ahmed; Saidi, Hamdani; Ahmad, Arshad

2011-11-01

218

Grafting of Methacrylonitrile and Ethyl Methacrylate onto Jute Fibre: Physico-chemical Characteristics of Grafted Jute  

NASA Astrophysics Data System (ADS)

Modification of bleached jute fibre was done by graft co-polymerization with vinyl monomers e.g. methacrylonitrile and ethyl methacrylate, in aqueous medium using H2O2-Na2S2O3 as redox initiators. To make the process efficient, the optimized polymerization condition was established. The maximum percent grafting and grafting efficiency obtained at optimum grafting condition were 11.3 and 20.4% for MAN, respectively and that of 17.6 and 27.5% for EMA. Modification of bleached jute fibre with MAN and EMA reduced the loss in breaking strength and the yellowing on exposure to sunlight in air.

Mondal, Md. Ibrahim H.; Islam Farouqui, Faisul; Abu Hanif, Md.; Shafiur Rahman, G. M.; Asadul Hoque, Md.

2005-10-01

219

Radiation-grafted proton exchange membranes based on co-grafting from binary monomer mixtures into poly(ethylene-co-tetrafluoroethylene) (ETFE) film  

NASA Astrophysics Data System (ADS)

In this study, proton exchange membranes (PEMs) based on a poly(ethylene-co-tetrafluoroethylene) (ETFE) film were synthesized through the graft copolymerization of styrene and VTMS (vinyltrimethoxysilane), or styrene and TMSPM (3-(trimethoxysilyl) propyl methacrylate) binary monomer systems using a simultaneous irradiation method. The prepared membranes with the similar degrees of grafting were investigated by measuring ion exchange capacity, proton conductivity, water uptake, chemical stability, and dimensional stability. The results indicate that the silane-crosslinked proton exchange membrane (PEM) has not only lower water uptake and dimensional change but also high proton conductivity at low humidity condition compared to non-crosslinked poly(ethylene-co-tetrafluoroethylene)-g-poly(styrene sulfonic acid) (ETFE-g-PSSA). Also, the chemical stability of silane-crosslinked fuel cell membranes was more improved than that of non-crosslinked fuel cell membrane.

Sohn, Joon-Yong; Sung, Hae-Jun; Song, Joo-Myung; Shin, Junhwa; Nho, Young-Chang

2012-08-01

220

Radiation-induced and RAFT-mediated grafting of poly(hydroxyethyl methacrylate) (PHEMA) from cellulose surfaces  

NASA Astrophysics Data System (ADS)

This paper presents the results of RAFT mediated free-radical graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto cellulose fibers in a "grafting-from" approach under ?-irradiation. The effects of absorbed dose and monomer concentration on the graft ratios were investigated at different monomer (HEMA) to RAFT agent (cumyl dithiobenzoate, CDB) ratios. Cellulose-g-PHEMA copolymers with various graft ratios up to 92% (w/w) have been synthesized. The synthesized copolymers were characterized by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy, elemental analysis and scanning electron microscopy. The results of various techniques confirmed the existence of PHEMA in the copolymer composition.

Kodama, Yasko; Barsbay, Murat; Güven, Olgun

2014-01-01

221

Synthesis of chemically cross-linked polyvinyl alcohol-co-poly (methacrylic acid) hydrogels by copolymerization; a potential graft-polymeric carrier for oral delivery of 5-fluorouracil  

PubMed Central

Background of the Study The propose of the present work was to develop chemically cross-linked polyvinyl alcohol-co-poly(methacrylic acid) hydrogel (PVA-MAA hydrogel) for pH responsive delivery of 5-Fluorouracil (5-FU). Methods PVA based hydrogels were prepared by free radical copolymerization. PVA has been cross-linked chemically with monomer (methacrylic acid) in aqueous medium, cross-linking agent was ethylene glycol di-methacrylate (EGDMA) and benzoyl peroxide was added as reaction initiator. 5-FU was loaded as model drug. FTIR, XRD, TGA and DSC were performed for characterization of copolymer. Surface morphology was studied by SEM. pH sensitive properties were evaluated by swelling dynamics and equilibrium swelling ratio at low and higher pH. Results FTIR, XRD, TGA and DSC studies confirmed the formation of new copolymer. Formulations with higher MAA contents showed maximum swelling at 7.4 pH. High drug loading and higher drug release has been observed at pH 7.4. Conclusions The current study concludes that a stable copolymeric network of PVA was developed with MAA. The prepared hydrogels were highly pH responsive. This polymeric network could be a potential delivery system for colon targeting of 5-FU in colorectal cancers. PMID:23721569

2013-01-01

222

Uranium Sorption by Pseudomonas Biomass Immobilized in Radiation Polymerized Polyacrylamide Bio-Beads  

Microsoft Academic Search

A Pseudomonas strain identified as a potent biosorbent of uranium (U) and thorium was immobilized in radiation-induced polyacrylamide matrix for its application in radionuclide containing wastewater treatment. The immobilized biomass exhibited a high U sorption of 202 mg g dry wt. with its optimum at pH 5.0. A good fit of experimental data to the Freundlich model suggested multilayered uranium

S. F. DSOUZA; PINAKI SAR; SUFIA K. KAZY; B. S. KUBAL

2006-01-01

223

Fixation of three-dimensional states of deformation in polymers by ionizing radiation. Search for new polymeric materials.  

NASA Astrophysics Data System (ADS)

The fixation of three-dimensional states of deformation in polymers allows the analysis of "special states" of elastic stresses even in the interior of complex constructional units and machine parts. This is the reason for the fact that in spite of the development of modern experimental methods of the analysis of deformation, which are in general restricted to the deformation of the surface of the bodies, the classical "photoelasticity" is still an adequate procedure for solving technical problems. However there are several restrictions on the applicability of the presently used procedures. A potential way to overcome these restrictions is the use of ionizing radiation, which in several polymeric materials causes a more or less perfect fixation of three-dimensional states of deformation. The search for suitable polymers includes the modification of well-known materials like epoxy resins as well as the application and development of materials not yet used in this field of engineering. Preliminary results of the search for such new materials are presented. In selected polymers the stress-optical constant f ? (S) typically increases with dose, whereas the optical creep behaves ambiguous on irradiation.

Schaudy, R.; Wendrinsky, J.; Beer, R. J.; Eberhardsteiner, J.

1995-02-01

224

The effect of nanocomposite polymeric layer on the radiation of antisymmetric zero-order Lamb wave in a piezoelectric plate contacting with liquid  

NASA Astrophysics Data System (ADS)

A nanocomposite polymeric layer is proposed to be used for increasing the efficiency of ultrasound radiation into the liquid by antisymmetric zero-order (A0) Lamb waves propagating in piezoelectric plates. The theoretical and experimental investigations of the influence of the nanocomposite polymeric layers on the efficiency and radiation angle of acoustic wave into liquid were carried out. It has been theoretically shown that the use of the layer of the polyethylene of low density with nanoparticles of cadmium sulfide of concentration 25% between the plate of 128YX LiNbO3 and water medium allows to increase the radiation attenuation on ˜1 dB/? if the ratio of the thicknesses of the layer and plate is equal to 0.16 at the frequency of 1.3 MHz. The experimental data were in a good agreement with theoretical results. It has been also shown that the presence of nanocomposite film leads to the increase of the radiation angle of bulk acoustic wave in liquid and allows the effective operation of the radiator not only in the sweet water but also in salt one. The obtained results may be used for the development of effective radiators/receivers of acoustic waves in liquids for flow meters and for underwater communication systems.

Kuznetsova, I. E.; Zaitsev, B. D.; Borodina, I. A.; Shikhabudinov, A. M.; Teplykh, A. A.; Manga, E.; Feuillard, G.

2013-06-01

225

Surface modification of polymeric materials using ultra low energy electron beam irradiation  

NASA Astrophysics Data System (ADS)

An ultra low energy electron beam (UL-EB) was used to irradiate various polymeric materials such as fluorinated polymers and a polyimide under an oxygen-free atmosphere. After the irradiation of the polyimide, the change in the thermal properties was measured by DSC and TGA. The surface modification of fluorinated polymers was demonstrated by use of styrene grafting by the preirradiation grafting method. By the use of UL-EB irradiation it was possible to facilitate styrene monomer grafting onto the surface of fluorinated polymers without losing their material characteristics. Moreover, in the case of the polyimide (Kapton™), which has excellent radiation resistance, the glass transition temperature was improved by about 20 °C by irradiation up to 40 MGy within 1 h.

Oshima, Akihiro; Shiraki, Fumiya; Fujita, Hajime; Washio, Masakazu

2011-02-01

226

Temperature-responsiveness and biocompatibility of DEGMA/OEGMA radiation-grafted onto PP and LDPE films  

NASA Astrophysics Data System (ADS)

Polypropylene (PP) and low density polyethylene (LDPE) were modified by ?-ray grafting of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo (ethylene glycol) methyl ether methacrylate (OEGMA300 or OEGMA475 with Mn 300 and 475 respectively) with different monomer concentrations and mol ratios. The grafting percentage was evaluated as a function of the solvent, irradiation dose, reaction time, temperature, and monomers concentration. The grafted materials were more hydrophilic than the pristine polymers, as observed by contact angle and swelling in water. Temperature-responsive behavior was evaluated using DSC showing transitions between 34 and 48 °C. In vitro hemocompatibility, protein adsorption, cytotoxicity and bacteria adhesion tests were also carried out. Overall, the DEGMA/OEGMA grafting provides hemo and cytocompatible materials that exhibit temperature-responsive hydrophilic features and decreased protein adsorption.

Ramírez-Jiménez, Alejandro; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2014-06-01

227

Radiation synthesis of multifunctional polymeric hydrogels for oral delivery of insulin.  

PubMed

Polyelectrolyte crosslinked hydrogel was synthesized using gamma radiation-induced copolymerization of methacrylic acid (MAA), N,N-dimethyl aminoethyl methacrylate (DMAEMA) in aqueous solution to utilize for oral delivery of insulin. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion in the glassy polymer was discussed. In addition, the swelling kinetics tests on MAA/DMAEMA (90/10) reveal that the swelling kinetics of the proposed hydrogel follows a Fickian diffusion process in media of pH 5, and an anomalous diffusion process in media of pH 1.5 and 7.2. The cross-linked three-dimensional polymers were characterized by scanning electron microscopy and FT-IR. In the matrices with increase in the content of MAA had shown increased bioadhesivity. Insulin was entrapped in these gels and the in vitro release profiles were established separately in both (SGF, pH 1.5) and (SIF, pH 7.2). The release profile of insulin showed negligible release in acidic media (SGF, pH 1.5) and sustained release in simulated intestinal fluid (SIF, pH 7.2). Drug release studies showed that the increasing content of MAA in the copolymer enhances release in SIF to design and improve insulin release behavior from these carriers. PMID:24055698

Abou Taleb, Manal F

2013-11-01

228

Physical properties of agave cellulose graft polymethyl methacrylate  

NASA Astrophysics Data System (ADS)

The grafting polymerization of methyl methacrylate and Agave cellulose was prepared and their structural analysis and morphology were investigated. The grafting reaction was carried out in an aqueous medium using ceric ammonium nitrate as an initiator. The structural analysis of the graft copolymers was carried out by Fourier transform infrared and X-ray diffraction. The graft copolymers were also characterized by field emission scanning electron microscopy (FESEM). An additional peak at 1732 cm-1 which was attributed to the C=O of ester stretching vibration of poly(methyl methacrylate), appeared in the spectrum of grafted Agave cellulose. A slight decrease of crystallinity index upon grafting was found from 0.74 to 0.68 for cellulose and grafted Agave cellulose, respectively. Another evidence of grafting showed in the FESEM observation, where the surface of the grafted cellulose was found to be roughed than the raw one.

Rosli, Noor Afizah; Ahmad, Ishak; Abdullah, Ibrahim; Anuar, Farah Hannan

2013-11-01

229

Physical properties of agave cellulose graft polymethyl methacrylate  

SciTech Connect

The grafting polymerization of methyl methacrylate and Agave cellulose was prepared and their structural analysis and morphology were investigated. The grafting reaction was carried out in an aqueous medium using ceric ammonium nitrate as an initiator. The structural analysis of the graft copolymers was carried out by Fourier transform infrared and X-ray diffraction. The graft copolymers were also characterized by field emission scanning electron microscopy (FESEM). An additional peak at 1732 cm{sup ?1} which was attributed to the C=O of ester stretching vibration of poly(methyl methacrylate), appeared in the spectrum of grafted Agave cellulose. A slight decrease of crystallinity index upon grafting was found from 0.74 to 0.68 for cellulose and grafted Agave cellulose, respectively. Another evidence of grafting showed in the FESEM observation, where the surface of the grafted cellulose was found to be roughed than the raw one.

Rosli, Noor Afizah; Ahmad, Ishak; Abdullah, Ibrahim; Anuar, Farah Hannan [Polymer Research Centre (PORCE), School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi Selangor (Malaysia)

2013-11-27

230

Standardization of procedures for ectopic marrow grafting. II. Influence on recipients of radiation dose and field size  

SciTech Connect

The ectopic implantation of mouse marrow to the kidney capsule offers considerable scope as an assay of the hemopoietic microenvironment. Our previous work has shown that whole-body irradiation of the graft recipient prior to implantation results in superior ossicle formation in the kidney of the host. Here we report that a range of irradiation doses over a 4-Gy threshold are equivalent with respect to conditioning the graft recipient. We also show that two distinct and separable influences affect graft growth in the irradiated recipient, namely, a local effect brought about in the irradiated kidney (and restricted to it) and secondly, a systemic effect resulting from irradiation of sites other than the kidney, which nevertheless affects ossicle growth in the shielded renal capsule.

Molineux, G.; Schofield, R.; Hendry, J.H.; Testa, N.G.

1987-07-01

231

Engineering Polymeric Scaffolds for Bone Grafts  

Microsoft Academic Search

Orthopedic injuries resulting from trauma or improper development often require surgical intervention to restore natural tissue function. Currently, over one million operations are performed annually for the surgical reconstruction of bone [50]. The well-known limitations associated with autografts, allografts, and bone cements have led to the investigation of synthetic polymers as support matrices for bone tissue engineering. Polymers are long-chain

Martha W. Betz; Diana M. Yoon; John P. Fisher

232

PP films grafted with N-isopropylacrylamide and N-(3-aminopropyl) methacrylamide by ? radiation: synthesis and characterization  

NASA Astrophysics Data System (ADS)

Simultaneous grafting of N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) on polypropylene (PP) was investigated for obtaining interfaces that are stimuli-responsive under physiological conditions. A pre-irradiation method was optimized tuning the ?-irradiation dose, reaction time, temperature, and monomers concentrations. FT-IR ATR and XPS analysis of the grafted copolymers evidenced a greater content in NIPAAm than in APMA; the APMA/NIPAAm ratio increasing with the concentration of APMA in the reaction medium and when the grafting was carried out in 1 M NaNO 3. The grafted films were characterized regarding their thermal properties (DSC and TGA) swelling behavior and contact angle. Immersion of the pre-irradiated films in 1 M NIPAAm/0.5 M APMA aqueous solution rendered PP-g-(1NIPAAm- r-0.5APMA) which exhibited rapid and reversible transitions showing a LCST around the physiological temperature. By contrast, a greater content in APMA enhanced the hydrophilicity and prevented the shrinking of PP-g-(1NIPAAm- r-1APMA).

Contreras-García, Angel; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2010-05-01

233

Preparation of quaternized dimethylaminoethylmethacrylate grafted nonwoven fabric for the removal of phosphate  

NASA Astrophysics Data System (ADS)

Dimethylaminoethylmethacrylate (DMAEMA) grafted polyethylene/polypropylene (PE/PP) nonwoven fabric was prepared by radiation-induced graft polymerization. Grafting conditions were optimized and about 150% DMAEMA grafted samples were used for further experiments. DMAEMA graft chains were later quaternized with dimethyl sulphate for the removal of phosphate ions. Adsorption experiments were conducted with quaternized DMAEMA grafted fabric for phosphate removal at low (0.5-25 ppm) and high phosphate concentrations (50-1000 ppm). Adsorbed phosphate amounts at pH 7 were found to be 63 mg phosphate/g polymer and 512 mg phosphate/g polymer for low (25 ppm) and high phosphate concentrations (1000 ppm) respectively showing the efficiency of the adsorbent material in removing phosphate. The pH effect on phosphate adsorption showed that the quaternized DMAEMA grafted nonwoven fabric can adsorb phosphate over a wide pH range (5.00-9.00) indicating that adsorbent material can effectively remove different forms of phosphate ions, namely H 2PO 4-, HPO 42- and PO 43- in aqueous solution at this pH range where the species exist. Competitive adsorption experiments were also carried out with two concentration levels at pH 7 to investigate the effect of competing ions. Phosphate adsorption on quaternized DMAEMA grafted nonwoven fabric was found to be higher than the other competing ions at two concentration levels. At high concentration level, the adsorption order was phosphate>nitrite>bromide>sulphate>nitrate whereas at low concentration level, the order was phosphate?sulphate>bromide>nitrite>nitrate.

Kavakl?, P?nar Akka?; Kavakl?, Cengiz; Güven, Olgun

2010-03-01

234

Effect of bidispersity in grafted chain length on grafted chain conformations and potential of mean force between polymer grafted nanoparticles in a homopolymer matrix  

NASA Astrophysics Data System (ADS)

In efforts to produce polymeric materials with tailored physical properties, significant interest has grown around the ability to control the spatial organization of nanoparticles in polymer nanocomposites. One way to achieve controlled particle arrangement is by grafting the nanoparticle surface with polymers that are compatible with the matrix, thus manipulating the interfacial interactions between the nanoparticles and the polymer matrix. Previous work has shown that the molecular weight of the grafted polymer, both at high grafting density and low grafting density, plays a key role in dictating the effective inter-particle interactions in a polymer matrix. At high grafting density nanoparticles disperse (aggregate) if the graft molecular weight is higher (lower) than the matrix molecular weight. At low grafting density the longer grafts can better shield the nanoparticle surface from direct particle-particle contacts than the shorter grafts and lead to the dispersion of the grafted particles in the matrix. Despite the importance of graft molecular weight, and evidence of non-trivial effects of polydispersity of chains grafted on flat surfaces, most theoretical work on polymer grafted nanoparticles has only focused on monodisperse grafted chains. In this paper, we focus on how bidispersity in grafted chain lengths affects the grafted chain conformations and inter-particle interactions in an implicit solvent and in a dense homopolymer polymer matrix. We first present the effects of bidispersity on grafted chain conformations in a single polymer grafted particle using purely Monte Carlo (MC) simulations. This is followed by calculations of the potential of mean force (PMF) between two grafted particles in a polymer matrix using a self-consistent Polymer Reference Interaction Site Model theory--Monte Carlo simulation approach. Monte Carlo simulations of a single polymer grafted particle in an implicit solvent show that in the bidisperse polymer grafted particles with an equal number of short and long grafts at low to medium grafting density, the short grafts are in a more coiled up conformation (lower radius of gyration) than their monodisperse counterparts to provide a larger free volume to the longer grafts so they can gain conformational entropy. The longer grafts do not show much difference in conformation from their monodisperse counterparts at low grafting density, but at medium grafting density the longer grafts exhibit less stretched conformations (lower radius of gyration) as compared to their monodisperse counterparts. In the presence of an explicit homopolymer matrix, the longer grafts are more compressed by the matrix homopolymer chains than the short grafts. We observe that the potential of mean force between bidisperse grafted particles has features of the PMF of monodisperse grafted particles with short grafts and monodisperse grafted particles with long grafts. The value of the PMF at contact is governed by the short grafts and values at large inter-particle distances are governed by the longer grafts. Further comparison of the PMF for bidisperse and monodisperse polymer grafted particles in a homopolymer matrix at varying parameters shows that the effects of matrix chain length, matrix packing fraction, grafting density, and particle curvature on the PMF between bidisperse polymer grafted particles are similar to those seen between monodisperse polymer grafted particles.

Nair, Nitish; Wentzel, Nathaniel; Jayaraman, Arthi

2011-05-01

235

Synthesis and characterization of radiation grafted films for removal of arsenic and some heavy metals from contaminated water  

NASA Astrophysics Data System (ADS)

Grafting of styrene/maleic anhydride and methyl methacrylate/maleic anhydride binary monomers onto the low density polyethylene film was performed using the ?-ray irradiation technique. Then, the synthesized grafted films were treated with different ammonia derivatives for developing chelating functionalization. These chelating products were characterized by the gravimetric method as well as by the Fourier transformed infrared spectroscopic method, and were used for removal of arsenic and some heavy metals from aqueous solutions. The optimum absorbed dose of 30 kGy reveals the graft yielding of about 325% in the films. Uptake of arsenic and some heavy-metal ions (Cr(III), Mn(II), Fe(III), Ni(II), Cu(II) and Pb(II)) from contaminated water by the chelating functionalized films (CFF) was examined by an atomic absorption spectrophotometer. The maximum arsenic removal capacity of 5062 mg/kg has been observed for the film treated with hydroxylamine hydrochloride. The CFF prepared by semicarbazide and thiol analogs show affinity toward the metal ions with an order: Cu(II)>Fe(III)>Mn(II) etc. The results obtained from this study indicate that the functionalized films show good chelating and ion-exchange property for metal ions.

Chowdhury, M. N. K.; Khan, M. W.; Mina, M. F.; Beg, M. D. H.; Khan, Maksudur R.; Alam, A. K. M. M.

2012-10-01

236

ROMP from ROMP: A New Approach to Graft Copolymer Synthesis.  

PubMed

A new strategy is presented for the synthesis of graft copolymers using only the ring-opening metathesis polymerization (ROMP). From a ROMP-derived main chain, pendant maleimide functional groups are converted into norbornene moieties via a Diels-Alder reaction with cyclopentadiene. The norbornene groups serve as sites of initiation, and subsequent ROMP from the main chain yields graft copolymers with both main and side chains derived from ROMP. This strategy offers ready access to defined graft copolymers. PMID:20161406

Allen, Matthew J; Wangkanont, Kittikhun; Raines, Ronald T; Kiessling, Laura L

2009-06-23

237

The time course of long-distance signaling in radiation-induced bystander effect in vivo in Arabidopsis thaliana demonstrated using root micro-grafting.  

PubMed

The radiation-induced bystander effect has been demonstrated in whole organisms as well as in multicellular tissues in vitro and single-cell culture systems in vitro. However, the time course of bystander signaling, especially in whole organisms, is not clear. Long-distance bystander/abscopal effects in vivo in plants have been demonstrated by our group. Plant grafting is a useful experimental tool for studying the root-shoot signaling of plants. In the present study, we developed a root micro-grafting technique with young seedlings of Arabidopsis thaliana in which the bystander signaling communication of root-to-shoot could easily be stopped or started at specific times after root irradiation. Using this methodology, we demonstrated the time course of long-distance signaling in radiation-induced bystander effects at the level of the organism using the expression level of the AtRAD54 gene as a biological end point. Briefly, an 8-h accumulation of damage signals in bystander parts after irradiation was essential for eliciting a bystander response. The protraction of signal accumulation was not related to the transmission speed of signaling molecules in plants and did not result from the delayed initiation of bystander signals in targeted root cells. It was suggested that the bystander effect might be induced jointly by multiple bystander signals initiated at different stages after irradiation. Moreover, reactive oxygen species (ROS) were shown to be implicated in the response process of bystander cells to radiation damage signals rather than in the generation of bystander signals in targeted cells. PMID:21574863

Wang, Ting; Li, Fanghua; Xu, Shuyan; Bian, Po; Wu, Yuejin; Wu, Lijun; Yu, Zengliang

2011-08-01

238

Synthesis of arsenic graft adsorbents in pilot scale  

NASA Astrophysics Data System (ADS)

Synthesis of arsenic (As) adsorbents in pilot scale was carried out with a synthesizing apparatus by radiation-induced graft polymerization of 2-hydroxyethyl methacrylate phosphoric acid monomer (PA), which consists of phosphoric acid mono- (50%) and di- (50%) ethyl methacrylate esters onto a nonwoven cotton fabric (NCF), and following chemical modification by contact with a zirconium (Zr) solution. The apparatus which was equipped with reaction tanks, a washing tank and a pump can produce up to 0.3 m×14 m size of the As(V) adsorbent in one reaction. A degree of grafting of 150% was obtained at an irradiation dose of 20 kGy with 5% of PA solution mixed with deionized water for 1 h at 40 °C. Finally, after Zr(IV) was loaded onto a NCF with 5 mmol/L of Zr(IV) solution, the graft adsorbent for the removal of As(V) was achieved in pilot-scale. The adsorbent which was synthesized in pilot scale was evaluated in batch mode adsorption with 1 ppm (mg/l) of As(V) solution for 2 h at room temperature. As a result, the adsorption capacity for As(V) was 0.02 mmol/g-adsorbent.

Hoshina, Hiroyuki; Kasai, Noboru; Shibata, Takuya; Aketagawa, Yasushi; Takahashi, Makikatsu; Yoshii, Akihiro; Tsunoda, Yasuhiko; Seko, Noriaki

2012-08-01

239

Polymerization and surface modification by low pressure plasma technique  

NASA Astrophysics Data System (ADS)

A durable water repellent, stain resistant or flame retardant character can be conferred to polyacrylonitrile (PAN) textiles by using the plasma induced graft polymerization technique. The monomers used are perfluoroalkylacrylate, (meth)acrylate phosphates, and phosphonates which are well known to be effective for the waterproofing and the fireproofing of polymeric substrates, respectively.

Tsafack, M.-J.; Hochart, F.; Levalois-Grützmacher, J.

2004-06-01

240

Polymeric nitrogen  

SciTech Connect

The equilibrium phase boundary between single-bonded, threefold-coordinated polymeric forms of nitrogen, and the observed, triple-bonded diatomic phases, is predicted to occur at relatively low (50[plus minus]15 GPa) pressure. This conclusion is based on extensive local-density-functional total-energy calculations for polymeric structures (including that of black phosphorus, and another with all [ital gauche] dihedral angles) and diatomic structures (including that of the observed high-pressure [var epsilon]-N[sub 2] phase). We believe the diatomic phase of nitrogen, observed up to 180 GPa and room temperature, to be metastable at these conditions, and that such hysteresis enhances the prospects for the existence of a metastable polymeric form of nitrogen at ambient conditions. In this regard, we show that the black-phosphorus and cubic [ital gauche] polymeric forms of nitrogen would encounter significant barriers along high-symmetry paths to dimerization at atmospheric pressure.

Mailhiot, C.; Yang, L.H.; McMahan, A.K. (Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States))

1992-12-01

241

Synthesis and characterization of superabsorbent polymer prepared by radiation-induced graft copolymerization of acrylamide onto carboxymethyl cellulose for controlled release of agrochemicals  

NASA Astrophysics Data System (ADS)

Superabsorbent polymer (SAP) was synthesized by radiation-induced grafting of acrylamide (AM) onto carboxymethyl cellulose (CMC) in the presence of a crosslinking agent, N,N?-methylenebisacrylamide (MBA). The effects of various parameters, such as dose, the amount of CMC, AM, MBA and ionic strength on the swelling ratio were investigated. In order to evaluate its controlled release potential, SAP was loaded with potassium nitrate (KNO3) as an agrochemical model and its potential for controlled release of KNO3 was studied. The amount of released KNO3 was analyzed by an inductively coupled plasma mass spectrometry (ICP-MS). The results from controlled release experiment agreed very well with the results from swelling experiment. The synthesized SAP was characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The obtained SAP exhibited a swelling ratio of 190 g/g of dry gel.

Hemvichian, Kasinee; Chanthawong, Auraruk; Suwanmala, Phiriyatorn

2014-10-01

242

Laundering durable antibacterial cotton fabrics grafted with pomegranate-shaped polymer wrapped in silver nanoparticle aggregations  

PubMed Central

To improve the laundering durability of the silver functionalized antibacterial cotton fabrics, a radiation-induced coincident reduction and graft polymerization is reported herein where a pomegranate-shaped silver nanoparticle aggregations up to 500?nm can be formed due to the coordination forces between amino group and silver and the wrapping procedure originated from the coincident growth of the silver nanoparticles and polymer graft chains. This pomegranate-shaped silver NPAs functionalized cotton fabric exhibits outstanding antibacterial activities and also excellent laundering durability, where it can inactivate higher than 90% of both E. coli and S. aureus even after 50 accelerated laundering cycles, which is equivalent to 250 commercial or domestic laundering cycles. PMID:25082297

Liu, Hanzhou; Lv, Ming; Deng, Bo; Li, Jingye; Yu, Ming; Huang, Qing; Fan, Chunhai

2014-01-01

243

Laundering durable antibacterial cotton fabrics grafted with pomegranate-shaped polymer wrapped in silver nanoparticle aggregations  

NASA Astrophysics Data System (ADS)

To improve the laundering durability of the silver functionalized antibacterial cotton fabrics, a radiation-induced coincident reduction and graft polymerization is reported herein where a pomegranate-shaped silver nanoparticle aggregations up to 500 nm can be formed due to the coordination forces between amino group and silver and the wrapping procedure originated from the coincident growth of the silver nanoparticles and polymer graft chains. This pomegranate-shaped silver NPAs functionalized cotton fabric exhibits outstanding antibacterial activities and also excellent laundering durability, where it can inactivate higher than 90% of both E. coli and S. aureus even after 50 accelerated laundering cycles, which is equivalent to 250 commercial or domestic laundering cycles.

Liu, Hanzhou; Lv, Ming; Deng, Bo; Li, Jingye; Yu, Ming; Huang, Qing; Fan, Chunhai

2014-08-01

244

Graft copolymers from poly(2,6-dimethylphenylene oxide) and pivalolactone  

SciTech Connect

The copolyether-polyester system resulting from the anionic graft polymerization of pivalolactone onto poly(2,6-dimethylphenylene oxide) has been formulated with differing graft densities and graft segment lengths. Wide angle X-ray scattering studies on these materials indicated an increased crystalline order with increased PVL segments/graft for similarly annealed specimens and a decrease in such order with increasing carboxylation. 10 references.

Bell, V.L.; Wakelyn, N.T.

1988-01-01

245

Olefin polymerization  

SciTech Connect

A process is described for producing high density and high flexural modulus olfin polymers comprising polymerizing the olefins in the presence of a catalyst composition. The composition comprises a chromium compound on a xerogel base comprising at least one of iron phosphate and iron polyphosphate and at least one of aluminium phosphate and aluminium polyphosphate.

McDaniel, M.P.

1986-11-11

246

Graft copolymerization of acrylonitrile onto bagasse and wood pulps  

SciTech Connect

Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50/sup 0/C than at 30/sup 0/C or at 40/sup 0/C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.

Heikal, S.O.; El-Kalyoubi, S.F.

1982-08-01

247

Proximal Tibial Bone Graft  

MedlinePLUS

... the Smaller Toes AOFAS / FootCareMD / Treatments Proximal Tibial Bone Graft Page Content What is a bone graft? Bone grafts may be needed for various ... the proximal tibia. What is a proximal tibial bone graft? Proximal tibial bone graft (PTBG) is a ...

248

Synthesis of graft polyrotaxane by simultaneous capping of backbone and grafting from rings of pseudo-polyrotaxane  

PubMed Central

Summary Graft polyrotaxanes, with poly(?-caprolactone) (PCL) graft chains on the ring components were synthesized by the simultaneous ring-opening polymerization of ?-caprolactone from both ends of the backbone polymer, an end-functionalized polyethylene glycol (PEG) and the formation of inclusion complexes with ?-cyclodextrin (?-CD). PEG with multiple functional groups at each end was prepared by the condensation of PEG-amine and D-gluconic acid; the PEG derivative formed an inclusion complex with ?-CD. The polymerization of multiple hydroxy groups at the backbone ends resulted in a star-shaped end group, which served as a bulky capping group to prevent dethreading. In contrast, PEG with only one hydroxy group at each end did not produce polyrotaxanes, indicating that single PCL chains were too thin to confine ?-CDs to the complex. In addition, the grafting polymerization proceeded properly only when robust hydrogen bonds formed between ?-CDs were dissociated using a basic catalyst. Since the dissociation also induced dethreading, kinetic control of the polymerization and dissociation were crucial for producing graft polyrotaxanes. Consequently, this three-step reaction yielded graft polyrotaxanes in a good yield, demonstrating a significant simplification of the synthesis of graft polyrotaxanes. PMID:25383129

Inoue, Katsunari; Kudo, Masabumi

2014-01-01

249

Immobilization and stabilization of papain on poly(hydroxyethyl methacrylate-ethylenglycol dimethacrylate) beads grafted with epoxy functional polymer chains via surface-initiated-atom transfer radical polymerization (SI-ATRP).  

PubMed

Poly(hydroxyethyl methacrylate-ethylen glycol dimethacrylate), p(HEMA-EGDMA), beads were prepared by suspension polymerization, and were decorated with fibrous poly(glycidyl methacrylate), p(GMA), via surface initiated-atom transfer radical polymerization (SI-ATRP). The functional epoxy groups of the beads were used for covalent immobilization of papain. The average amount of immobilized enzyme was 18.7 mg/g beads. The immobilized enzyme was characterized by temperature, pH, operational and storage stability experiments. The maximum velocity of the free and immobilized enzymes (V(max)) and Michaelis-Menten constant (K(m)) values were determined as 10.7 and 8.3 U/mg proteins and 274 and 465 ?M, respectively. The immobilized papain was operated in a batch reactor, and it was very effective for hydrolysis of different proteins (i.e., casein and cytochrom c). PMID:21908189

Bayramoglu, Gulay; Senkal, B Filiz; Yilmaz, Meltem; Arica, M Yakup

2011-11-01

250

An empirical study into the effect of long term storage (-36±2 °C) of electron-beamed ETFE on the properties of radiation-grafted alkaline anion-exchange membranes  

NASA Astrophysics Data System (ADS)

The application of alkaline anion-exchange membranes (AAEM) in solid alkaline fuel cells is growing in prominence mainly due to enhanced tolerance to carbon dioxide, compared to alkaline fuel cells containing aqueous electrolytes, and the potential for using non precious metal catalysts. Radiation grafting is a common methodology for the production of functional polymers and membranes. This statistical study examines the synthesis of radiation grafted AAEMs that are formed from electron beam irradiated poly(ethylene-co-tetrafluoroethylene), EB-ETFE. It is shown that EB-ETFE can be cold stored for at least 16 months and still be used to produce ionically conductive AAEMs. The limitations of routine measurements of properties, such as dimensional increases, ion-exchange capacity, water uptakes and ionic conductivities, are also highlighted.

Kizewski, Jamie Peter; Mudri, Nurul H.; Varcoe, John R.

2013-08-01

251

Bone Graft Alternatives  

MedlinePLUS

... or during a surgical procedure such as spinal fusion. What Types of Bone Grafts are There? Bone ... bone grafts in spine surgery is during spinal fusion. The use of autogenous bone grafts for spinal ...

252

Radiation-chemical synthesis of polypropylene fabrics with sulfonic acid functional groups  

NASA Astrophysics Data System (ADS)

A sorption-active material carrying sulfonic acid groups was synthesized by the radiation-induced graft polymerization of styrene monomer onto the surface of non-woven polypropylene fabric, followed by sulfonation of the grafted polystyrene chains. The effect of the main experimental parameters (absorbed dose, monomer concentration, reaction time) on the styrene degree of grafting was investigated. The sulfonation process with 5% chlorosulfonic acid at room temperature was investigated in detail and the optimal sulfonation conditions for the samples with a medium degree of grafting (70-140%) were determined. Densities of 3.5-5 meq/g were obtained by applying those sorption-active PP fabrics with a sulfonic acid group.

Cho, Hyun Kug; Park, Jung Soo; Han, Do Hung; Bondar, Iuliia

2011-04-01

253

Chronic graft-versus-host disease in the rat radiation chimera: I. clinical features, hematology, histology, and immunopathology in long-term chimeras  

SciTech Connect

The clinical features, pathology, and immunopathology of chronic graft-versus-host disease (GVHD) developing in the long-term rat radiation chimera are described. At 6 to 12 months post-transplant, the previously stable ACI/LEW chimeras developed patchy to diffuse severe hair loss and thickened skin folds, and had microscopic features resembling scleroderma, Sjogren's syndrome, and chronic hepatitis. Skin histology showed dermal inflammation and acanthosis with atrophy of the appendages, with progression to dermal sclerosis. The liver revealed chronic hepatitis with bile duct injury and proliferation and periportal piecemeal necrosis. The tongue had considerable submucosal inflammation, muscular necrosis, and atrophy and arteritis. The serous salivary glands, lacrimal glands, and bronchi had lymphocytic inflammation and injury to duct, acinar, and mucosal columnar epithelium. The thymus had lymphocyte depletion of the medulla with prominent epithelium. The spleen and lymph nodes had poorly developed germinal centers but increased numbers of plasma cells. IgM was observed along the basement membrane and around the basal cells of the skin and tongue and along the basement membrane of the bile ducts. IgM was present also in the arteries of the tongue. Immunoglobulins eluted from the skin, cross-reacted with the bile duct epithelium and usually with both ACI and Lewis skin. Increased titers of speckled antinuclear antibodies were present in the serum of rats with chronic (GVHD). Chronic GVHD in the long-term rat radiation chimera is very similar to human chronic GVHD and is a potentially excellent model for autoimmune disorders including scleroderma, Sjorgren's syndrome, and chronic hepatitis.

Beschorner, W.E.; Tutschka, P.J.; Santos, G.W.

1982-04-01

254

Microwave initiated synthesis and application of polyacrylic acid grafted carboxymethyl cellulose  

Microsoft Academic Search

An environmentally benign and efficient route of synthesis of polyacrylic acid grafted carboxymethyl cellulose (CMC-g-PAA) is developed using microwave radiation alone to initiate the grafting reaction. The synthesis is optimized in terms of percentage grafting and intrinsic viscosity, by varying the microwave irradiation time and monomer (acrylic acid) concentration. The grafted product has been characterized by various physicochemical characterization techniques

Sumit Mishra; G. Usha Rani; Gautam Sen

255

Preparation and characterization of chemically stable polymer electrolyte membranes by radiation-induced graft copolymerization of four monomers into ETFE films  

Microsoft Academic Search

To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell (DMFC), four styrene derivative monomers, m,p-methylstyrene (MeSt), p-tert-butylstyrene (tBuSt), divinylbenzene (DVB) and bis(p,p-vinyl phenyl) ethane (BVPE) were graft copolymerized into poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by sulfonation and hydrolysis. The latter two monomers were used as crosslinkers. The graft copolymerization was carried out by

Jinhua Chen; Masaharu Asano; Tetsuya Yamaki; Masaru Yoshida

2006-01-01

256

Photoactivated surface grafting from PVDF surfaces  

NASA Astrophysics Data System (ADS)

Economic and easy methods to tune surface properties of polymers as Poly(vinylidene fluoride) (PVDF) without altering bulk properties are of major interest for different applications as biotechnological devices, medical implant device… UV irradiation appears as one of the simplest, easy and safe method to modify surface properties. In the case of self-initiated grafting, it is generally assumed that the pre-treatment of the PVDF surface with UV irradiation can yield alkyl and per-oxy radicals originating from breaking bonds and capable of initiating the subsequent surface grafting polymerizations. Surprisingly, the present work shows that it is possible to obtain polymer grafting using low energetic UV-A irradiation (3.1-3.9 eV) without breaking PVDF bonds. An EPR study has been performed in order to investigate the nature of involved species. The ability of the activated PVDF surface to graft different kinds of hydrophilic monomers using the initiated surface polymerization method has been tested and discussed on the basis of ATR FT-IR, XPS and NMR HRMAS results.

Berthelot, Thomas; Le, Xuan Tuan; Jégou, Pascale; Viel, Pascal; Boizot, Bruno; Baudin, Cécile; Palacin, Serge

2011-09-01

257

"Wet to dry" conformational transition of polymer layers grafted to nanoparticles in nanocomposite  

E-print Network

corona grafted around silica nano particles dispersed inside a nanocomposite, a matrix of the same prediction, this result constitutes a new insight for the understanding of the general problem of dispersion processes of controlled polymerization to obtain well defined grafted nano particles1 . Depending

Paris-Sud XI, Université de

258

Modification of Silica Nanoparticles by Grafting of Copolymers Containing Organosilane and Fluorine Moities.  

E-print Network

in a polymerization process. Most often, fluorinated silica nanoparticles are obtained either by a sol-gel process1 Modification of Silica Nanoparticles by Grafting of Copolymers Containing Organosilane(TMSPMA-stat-PFDA) cotelomers, containing fluoro and silane groups, were then grafted onto silica nanoparticles. Optimal

Boyer, Edmond

259

Grafting of a LLDPE using gamma irradiation  

NASA Astrophysics Data System (ADS)

In this investigation, the grafting of a commercial linear low-density polyethylene (LLDPE) with different concentrations of diethyl maleate (DEM, 5 and 15 wt.%) was carried out at different absorbed doses from a cobalt-60 source of gamma rays (0, 15, 30, 50, 100, 200 kGy). This process was performed in a decalin solution at 10% w/v to obtain a homogeneous dispersion of the monomer into the polyethylene matrix. The grafting degree was estimated by means of FTIR using a calibration curve reported in literature. Thermal properties of the functional polymers were studied by thermogravimetric analysis (TGA). Melt flow index (MFI) values were also taken. The results found indicate that the grafting degree increases as the concentration of DEM in the reaction mixture and the absorbed doses are increased upto 100 kGy, as expected. However, the behavior at higher doses is attributed to secondary reactions such as long-chain branching and/or crosslinking, which are faster than radical reactions responsible for the grafting of the DEM onto the polymeric chain. This fact was ascertained by the decrease of the MFI values as the applied irradiation was increased, irrespective of the quantity of DEM used in the grafting reaction. Therefore, in order to obtain a high grafting degree, the absorbed dose should be estimated carefully. Initial degradation temperatures of the grafted PEs decreased when the gamma irradiation dose was higher than 100 kGy. This indicates that the thermal stability decreases as higher doses are applied to the material, which is associated to branching and crosslinking. The grafting degree never exceeded 0.3 mol%, which demonstrates the low efficiency of the functionalization procedure here presented.

Catarí, E.; Albano, C.; Karam, A.; Perera, R.; Silva, P.; González, J.

2005-07-01

260

Two Photon Polymerization of Ormosils  

NASA Astrophysics Data System (ADS)

In this work, 3D structures of hybrid polymers—ORMOSILS (organically modified silicates) were produced via Two Photon Polymerization (2PP) of hybrid methacrylates based on silane derivates. Synthetic routes have been used to obtain series of hybrid monomers, their structure and purity being checked by NMR Spectroscopy and Fourier Transform Infrared Spectroscopy. Two photon polymerization method (a relatively new technology which allows fast micro and nano processing of three-dimensional structures with application in medical devices, tissue scaffolds, photonic crystals etc) was used for monomers processing. As laser a Ti: Sapphire laser was used, with 200 fs pulse duration and 2 kHz repetition rate, emitting at 775 nm. A parametric study on the influence of the processing parameters (laser fluence, laser scanning velocity, photo initiator) on the written structures was carried out. The as prepared polymeric scaffolds were tested in mesenchymal stem cells and fibroblasts cell cultures, with the aim of further obtaining bone and dermal grafts. Cells morphology, proliferation, adhesion and alignment were analyzed for different experimental conditions.

Matei, A.; Zamfirescu, M.; Jipa, F.; Luculescu, C.; Dinescu, M.; Buruiana, E. C.; Buruiana, T.; Sima, L. E.; Petrescu, S. M.

2010-10-01

261

Electrostrictive Graft Elastomers  

NASA Technical Reports Server (NTRS)

An electrostrictive graft elastomer has a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules. The polar graft moieties have been rotated by an applied electric field, e.g., into substantial polar alignment. The rotation is sustained until the electric field is removed. In another embodiment, a process for producing strain in an elastomer includes: (a) providing a graft elastomer having a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules; and (b) applying an electric field to the graft elastomer to rotate the polar graft moieties, e.g., into substantial polar alignment.

Su, Ji (Inventor); Harrison, Joycelyn S. (Inventor); St.Clair, Terry L. (Inventor)

2003-01-01

262

Polymer Grafted Janus Multi-Walled Carbon Nanotubes  

SciTech Connect

We describe a novel and facile strategy to modify the surface of carbon nanotubes (CNTs) with two chemically different polymer brushes utilizing the grafting from technique. A [4 + 2] Diels Alder cycloaddition reaction was used to functionalize multi-walled carbon nanotubes (MWNTs) with two different precursor initiators, one for ring opening polymerization (ROP) and one for atom transfer radical polymerization (ATRP). The binary functionalized MWNTs were used for the simultaneous surface initiated polymerizations of different monomers resulting in polymer grafted MWNTs that can form Janus type structures under appropriate conditions. 1H NMR, FTIR and Raman spectra showed that the precursor initiators were successfully synthesized and covalently attached on the CNT surface. Thermogravimetric analysis (TGA) revealed that the grafted polymer content varies when different monomer ratios and polymerization times are used. The presence of an organic layer around the CNTs was observed through transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) proved that the glass transition (Tg) and melting (Tm) temperatures of the grafted polymers are affected by the presence of the CNTs, while circular dichroism (CD) spectra indicated that the PLLA ahelix conformation remains intact.

Priftis, Dimitrios [ORNL; Sakellariou, Georgios [ORNL; Baskaran, Durairaj [University of Tennessee, Knoxville (UTK); Mays, Jimmy [ORNL; Hadjichristidis, Nikos [University of Athens, Athens, Greece

2009-01-01

263

A study on the distribution of polystyrene sulfonic acid grafts over the cross-section of a PFA film  

NASA Astrophysics Data System (ADS)

In this study, the distribution behaviors of polystyrene sulfonic acid (PSSA) grafts over the cross-section of grafted PFA membranes (PFA- g-PSSA) were investigated by using SEM-EDX analysis. Membranes with various degrees of grafting (DOG) and thicknesses were prepared by a simultaneous radiation grafting of styrene and a subsequent sulfonation with chlorosulfonic acid. A SEM-EDX instrument was utilized to directly observe that the distribution behaviors of the PSSA grafts over the cross-section of grafted PFA membranes and the results showed that the distribution behaviors were largely affected by the grafting conditions such as the degree of grafting, monomer concentration, and film thickness.

Shin, Junhwa; Ko, Beom-Seok; Kang, Sung-A.; Fei, Geng; Nho, Young-Chang; Kang, Phil-Hyun

2009-03-01

264

Polymerization of perfluorobutadiene at near-ambient conditions  

NASA Technical Reports Server (NTRS)

Peroxide catalyst under mild conditions initiates homopolymerization of perfluoro butadiene to new linear perfluoro polyenes and vulcanizable fluoro elastomers. Resulting polyperfluoro butadiene serves as hard elastomer for good chemical resistance, as intermediate in graft polymerizations, and as crosslink for high molecular weight materials.

Toy, M. S.

1971-01-01

265

Preparation of functional composite grafted particles PDMAEMA/SiO 2 and preliminarily study on functionality  

NASA Astrophysics Data System (ADS)

Micron-sized silica gel particles were first surface-modified with coupling agent, ?-methacryloylpropyl trimethoxysilane (MPS), and the polymerizable double bonds were introduced onto the surfaces of silica gel particles, forming the modified particles MPS-SiO 2. Subsequently, N,N-dimethylaminoethyl methacrylate (DMAEMA) was graft-polymerized on the surfaces of particles MPS-SiO 2 in the manner of "grafting through", resulting in the grafted particles PDMAEMA/SiO 2. The grafted particles PDMAEMA/SiO 2 were fully characterized with several means. The graft polymerization process of DMAEMA on particles MPS-SiO 2 was studied in detail, and the optimal reaction conditions were determined. Thereafter, the adsorption properties of the grafted particles PDMAEMA/SiO 2 for chromate anion and Cu 2+ ion were preliminarily examined respectively. The experimental results indicate that the PDMAEMA grafting degree on PDMAEMA/SiO 2 particles is limited because an enwinding polymer layer as a kinetic barrier on the surfaces of silica gel particles will be formed during the graft polymerization, and blocks the graft polymerization. In order to enhance PDMAEMA grafting degree, reaction time and temperature, and the used amount of initiator as well as the monomer concentration should be effectively controlled. The preliminary adsorption tests show that the grafted particles PDMAEMA/SiO 2 are multi-functional. They possess very strong adsorption ability for CrO 42- anion by right of strong electrostatic interaction, and have also adsorption action towards heavy metal ion by dint of complexing action.

Gao, Baojiao; Chen, Yinxin; Zhang, Zhenguo

2010-10-01

266

Preparation of poly(ether ether ketone)-based polymer electrolytes for fuel cell membranes using grafting technique  

Microsoft Academic Search

Poly(ether ether ketone) (PEEK)-based polymer electrolyte membranes (PEMs) was successfully prepared by radiation grafting of a styrene monomer into PEEK films and the consequent selective sulfonation of the grafting chains in the film state. Using milder sulfonation, the sulfonation reactions proceeded at the grafted chains in preference to the phenylene rings of PEEK main chains; as a result, the grafted

Shin Hasegawa; Yasuyuki Suzuki; Yasunari Maekawa

2008-01-01

267

Chemistry and technology of radiation processed composite materials  

NASA Astrophysics Data System (ADS)

Composite materials of synthetics (based on monomers, oligomers and thermoplastics) and of natural polymers (wood and other fibrous cellulosics) prepared by radiation processing, offer valuable structural materials with enhanced coupling forces between the components. The applied polymer chemistry of such composites shows several common features with that of radiation grafting. E.g. the polymerization rate of oligomer-monomer mixtures in wood remains in most cases proportional to the square-root of the initiating dose-rate, just as in the simultaneous grafting, demonstrating that the chain termination kinetics remain regularly bimolecular in the corresponding dose-rate ranges. In the processing experiences of such composites, low dose requirement, easy process-control, and good technical feasibility have been found for composites of wood with oligomer-monomer mixtures, for coconut fibres with unsaturated polyesters and for pretreated wood fibre with polypropylene.

Czvikovszky, T.

268

Polymeric Materials for Tissue Engineering of Arterial Substitutes  

PubMed Central

Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute. PMID:19426609

Ravi, Swathi; Qu, Zheng; Chaikof, Elliot L.

2009-01-01

269

Gamma-radiation-induced grafting of binary mixture of methacrylic acid and 4-vinyl pyridine onto Teflon-FEP film as an effective polar membrane for separation processes  

NASA Astrophysics Data System (ADS)

Ionic bifunctional membranes have been synthesized by grafting binary mixture of methacrylic acid (MAAc) and 4-vinyl pyridine (4-VP) onto Teflon-FEP film by pre-irradiation method. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of binary mixture (MAAc-co-4-VP) (71.29%) was obtained at an optimum total dose of 54.48 kGy and the total concentration was 9.49 mol/L ([4-VP] = 0.07 mol/L and [MAAc ] = 9.42 mol/L) in 5 ml of water. The effect of alcohols as additives to the reaction medium on percent grafting of the binary mixture has also been studied. The membranes were characterized by FTIR spectroscopy, scanning electron microscopy and thermogravimetric analysis. Swelling studies of the membranes were performed in different solvents such as water, benzene, carbon tetrachloride and dimethyl formamide (DMF). Maximum swelling was observed in DMF with minimum swelling in benzene. Metal ion (Cu 2+, Ni 2+ and Fe 2+) uptake studies show better affinity for Fe 2+ ions. Conductance measurements in different aqueous salt solution showed that these membranes have affinity for Na +/K + ions and Cl - ions and hence can be used in desalination/separation processes for the separation of both type of cationic and anionic ions.

Kaur, Inderjeet; Rattan, Sunita; Chauhan, Sandeep; Gupta, Nitika

2010-05-01

270

Polymeric materials in Space  

NASA Astrophysics Data System (ADS)

Paper of short review type. It is the continuation of and addition to previous review papers "V. E. Skurat. Polymers in Space. In: Encyclopedia of aerospace engineering, vol. 4, Wiley and sons, 2010; Ibid., 2012 (on line)". Following topics are considered: (1) Destruction of polymers by solar radiation with various wavelengths in different spectral regions (visible-UV, vacuum UV (VUV), deep UV, soft and hard X-rays) are discussed. In difference with common polymer photochemistry induced by UV radiation, directions of various routs of polymer phototransformations and their relative yields are greatly dependent on wavelength of light (photon energy) during illuminations in VUV, deep UV and X-ray regions. During last twenty years, intensive spacecraft investigations of solar spectrum show great periodic and spontaneous variations of radiation intensities in short-wavelengths regions - up to one - two decimal orders of magnitude for X-rays. As a result, during solar flares the absorbed dose on the polymer surfaces from X-rays can be compared with absorbed dose from VUV radiation. (2) Some new approaches to predictions of reaction efficiencies of fast orbital atomic oxygen in their interaction with polymeric materials are considered. (3) Some aspects of photocatalitic destruction of polymers in vacuum conditions by full-spectrum solar radiation are discussed. This process can take place in enamels containing semiconducting particles (TiO2, ZnO) as pigments. (4) Contamination of spacecraft surfaces from intrinsic outer atmosphere play important role not only from the point of view of deterioration of optical and thermophysical properties. Layers of SiO2 contaminations with nanometer thicknesses can greatly diminish mass losses from perfluorinated polymers under VUV irradiation.

Skurat, Vladimir

271

Polymerization of perfluorobutadiene  

NASA Technical Reports Server (NTRS)

Diisopropyl peroxydicarbonate dissolved in liquid perfluorobutadiene is conducted in a sealed vessel at the autogenous pressure of polymerization. Reaction temperature, ratio of catalyst to monomer, and amount of agitation determine degree of polymerization and product yield.

Newman, J.; Toy, M. S.

1970-01-01

272

Ring opening metathesis polymerization  

Microsoft Academic Search

This article intends to provide the reader with a basic knowledge of Ring Opening Metathesis Polymerization. Some historic background, mechanistic aspects, living polymerization, as well as current catalyst development and new applications are discussed.

Marcelo E. Piotti

1999-01-01

273

Influence of physical parameters on mutual polymer grafting by electron beam irradiation  

NASA Astrophysics Data System (ADS)

Grafting is a good method for modifying a polymer matrix and radiation induced grafting is an advantageous technique for chemical grafting because it does not require an initiator. In this work, mutual radiation grafting was performed and physical parameters like vacuum, pressure of air or inert gas and temperature were studied to verify their influences on styrene grafting onto hydrocarbon and fluorinated polymers. We observed that vacuum and temperature are determinant parameters to be considered in mutual radiation grafting besides the backbone polymer, monomer molecules and solvent. The optimization of these parameters for a specific polymer/monomer system contributes to a good performance and allows mutual radiation grafting to be an attractive technique even if it is performed in commercial accelerators.

Moura, E.; Somessari, E. S. R.; Silveira, C. G.; Paes, H. A.; Souza, C. A.; Fernandes, W.; Manzoli, J. E.; Geraldo, A. B. C.

2011-02-01

274

Redo aortic grafting after treatment of aortic graft infection  

Microsoft Academic Search

Purpose: This study was performed to determine the indications, operative strategy, and hemodynamic benefit of redo aortic grafting procedures after earlier excision of an infected aortic graft.Methods: Among 164 patients treated for aortic graft infection, 15 later underwent redo aortic grafting procedures an average of 18 months (range, 1 to 59 months) after removal of an infected aortic graft. Redo

Paul J. DiMuzio; Linda M. Reilly; Ronald J. Stoney

1996-01-01

275

Chemoenzymatic synthesis and hydrogelation of amylose-grafted xanthan gums.  

PubMed

This paper reports the chemoenzymatic synthesis of an amylose-grafted xanthan gum. An amine-functionalized maltooligosaccharide was chemically introduced to xanthan gum by condensation with its carboxylates using a condensing agent to produce a maltooligosaccharide-grafted xanthan gum. Then, a phosphorylase-catalyzed enzymatic polymerization of glucose 1-phosphate from the graft chain ends on the xanthan gum derivative was performed, giving an amylose-grafted xanthan gum. Furthermore, the product formed a gel with an ionic liquid, which was converted into a hydrogel with high water content by replacement of the ionic liquid with water. The ionically cross-linked hydrogel was also provided by soaking the primary formed hydrogel in FeCl(3) aqueous solution. The mechanical properties of the resulting hydrogels were evaluated by compressive testing. PMID:21689681

Arimura, Takuya; Omagari, Yuji; Yamamoto, Kazuya; Kadokawa, Jun-ichi

2011-11-01

276

Monolithic molecularly imprinted polymeric capillary columns for isolation of aflatoxins.  

PubMed

Monolithic molecularly imprinted polymers extraction columns have been prepared in fused-silica capillaries by UV or thermal polymerization in a two-step process. First, a poly-(trimethylolpropane trimethacrylate) (polyTRIM) core monolith was synthesized either by UV or thermal polymerization. Then it was grafted with the mixture of methacrylic acid (MAA) as a functional monomer, ethylene dimethacrylate (EDMA) as a cross-linking agent, 5,7-dimethoxycoumarin (DMC) as an aflatoxin-mimicking template, toluene as a porogen solvent and 2,2-azobis-(2-methylpropionitrile) (AIBN) as an initiator of the polymerization reaction. Different thermal condition of the photografting and different concentrations of the grafting mixture were tested during polymerization. The extraction capillary columns were evaluated in the terms of their hydrodynamic and chromatographic properties. Retention coefficients for aflatoxin B1 and DMC were used for assessment of the selectivity and imprinting factor. The obtained results indicate that the temperature of photografting and concentration of the grafting mixture are key parameters that determine the quality of the prepared MIPs. From the MIP columns characterized by the highest permeability the column of the highest imprinting factor was applied for isolation of aflatoxins B1, B2, G1 and G2 from the model aqueous sample followed by on-line chromatographic separation. The process was performed using a micro-MISPE-microLC-LIF system of a novel design, which allowed for detection of the eluates from the sample preparation part as well as from the chromatographic separation. PMID:25218633

Szumski, Micha?; Grzywi?ski, Damian; Prus, Wojciech; Buszewski, Bogus?aw

2014-10-17

277

Characterization of preirradiation grafting of acrylamide onto nylon-6 fabric  

NASA Astrophysics Data System (ADS)

The graft copolymerization of aqueous solutions containing acrylamide (AAm) onto nylon-6 fabric using the preirradiation technique has been studied. It was found that the addition of 0.05 wt% of ammonium iron II sulphate reduced effectively the homopolymer formation of AAm. The different factors that may influence the grafting reaction were investigated. The dependence of the grafting rate on the monomer concentration and the preirradiation dose was found to be 1.3 and 0.98 order, respectively. The study of the effect of reaction temperature revealed that the calculated overall activation energy for the graft polymerization of AAm onto nylon-6 are 55.3 and 32.4 kJ/mole below and above 60°C, respectively. The nylon-6 fabric grafted with acrylamide showed a significant increase in hydrophilic properties in terms of moisture and water regain as well as water absorption. Moreover, these properties were greatly enhanced when nylon-6 graft copolymers were dissolved in formic acid and subsequently converted into films. In addition, the dyeing properties of the produced graft copolymers indicate good dye affinity for selected dyestuffs. Finally, the values of the melting point, extent of crystallinity and glass transition were also investigated.

El-Naggar, A. M.; El-Salmawi, K.; Ibraheim, S. M.; Zahran, A. H.

1997-02-01

278

Hydroxyalkylation and polyether polyol grafting of graphene tailored for graphene/polyurethane nanocomposites.  

PubMed

Graphene functionalization by hydroxyalkylation and grafting with polyether polyols enables polyurethane (PU) nanocomposites formation by in situ polymerization with isocyanates combined with effective covalent interfacial coupling. Functionalized graphene (FG) hydroxylation is achieved either by alkylation, transesterification, or grafting of thermally reduced graphite oxide. In the presence of K2 CO3 as catalyst the reaction of FG-OH with ethylene carbonate at 180 °C affords hydroxyethylated FG, whereas transesterification with castor oil produces riconoleiate-modified FG polyols. In the "grafting-from" process, FG-alkoholate macro initiators initiate the graft polymerization of propylene oxide to produce hybrid FG polyols containing 38 and 59 wt% oligopropylene oxide. In the "grafting-to" process 3-ethyl-3-hydroxymethyl-oxetane is cationically polymerized onto FG-OH, producing novel hyperbranched FG-based polyether polyols. Whereas hydroxylation and grafting of FG greatly improve FG dispersion in organic solvents, polyols and even PU, as confirmed by transmission electron microscopy, matrix reinforcement of FG/PU is impaired by increasing alkyl chain length and polyol graft copolymer content. PMID:23836705

Appel, Anna-Katharina; Thomann, Ralf; Mülhaupt, Rolf

2013-08-01

279

The preparation of graft copolymers of cellulose and cellulose derivatives using ATRP under homogeneous reaction conditions.  

PubMed

In this comprehensive review, we report on the preparation of graft-copolymers of cellulose and cellulose derivatives using atom transfer radical polymerization (ATRP) under homogeneous conditions. The review is divided into four sections according to the cellulosic material that is graft-copolymerised; (i) cellulose, (ii) ethyl cellulose, (iii) hydroxypropyl cellulose and (iv) other cellulose derivatives. In each section, the grafted synthetic polymers are described as well as the methods used for ATRP macro-initiator formation and graft-copolymerisation. The physical properties of the graft-copolymers including their self-assembly in solution into nanostructures and their stimuli responsive behaviour are described. Potential applications of the self-assembled graft copolymers in areas such as nanocontainers for drug delivery are outlined. PMID:25016958

Joubert, Fanny; Musa, Osama M; Hodgson, David R W; Cameron, Neil R

2014-09-22

280

Encapsulation of bovine serum albumin within ?-cyclodextrin\\/gelatin-based polymeric hydrogel for controlled protein drug release  

Microsoft Academic Search

Novel biodegradable pH-responsive polymeric hydrogels based on ?-cyclodextrin (?-CD) and gelatin (G) were prepared for controlled protein drug delivery studies. The polymeric hydrogels, G-g-poly(GMA) were obtained by grafting copolymerization of glycidyl methacrylate monomer (GMA) onto gelatin in presence of ammonium ceric nitrate (CAN) as initiator. Immobilization of ?-CD onto G-g-poly(GMA) hydrogel was then carried out. The prepared polymeric hydrogels were

A. A. Haroun; N. R. El-Halawany

2010-01-01

281

PVDF multifilament yarns grafted with polystyrene induced by ?-irradition: Influence of the grafting parameters on the mechanical properties  

NASA Astrophysics Data System (ADS)

The development of alternative prosthetic materials for cardiovascular applications has found growing interest due to the failure to date to be able to implement functional patent small diameter vascular grafts (?<5 mm). For instance, the successful implantation of small diameter polyester (PET) and expanded polytetrafluoroethylene (PTFEe) vascular grafts has not been achieved in humans. Our stategy is to work with a new multifilament yarns biomaterial, produced from polyvinylidene fluoride (PVDF), which shows suitable mechanical properties, such as a lower tensile modulus than PET and PTFEe. The required biological properties sought for (i.e. low thrombogenicity) could be achieved by "heparin-like" surface modification treatments in order to modify the thrombogenicity levels of the polymeric materials [Ann. Biomed. Eng. 7 (1979) 429]. A four step method is necessary to achieve this "heparin-like" surface transformation [J. Biomed. Mater. Res. 52 (2000) 119]. The first step consists in grafting polystyrene onto the PVDF surface by ? irradiation. The purpose of this study was to evaluate the influence of grafting parameters on the mechanical properties: (i) ?-ray irradiation time and (ii) grafting time of styrene monomers, which polymerize and form polystyrene bound to the PVDF surface.

Marmey, P.; Porté, M. C.; Baquey, Ch.

2003-08-01

282

A Versatile Star PEG Grafting Method for the Generation of Nonfouling and Nonthrombogenic Surfaces  

PubMed Central

Polyethylene glycol (PEG) grafting has a great potential to create nonfouling and nonthrombogenic surfaces, but present techniques lack versatility and stability. The present work aimed to develop a versatile PEG grafting method applicable to most biomaterial surfaces, by taking advantage of novel primary amine-rich plasma-polymerized coatings. Star-shaped PEG covalent binding was studied using static contact angle, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Fluorescence and QCM-D both confirmed strong reduction of protein adsorption when compared to plasma-polymerized coatings and pristine poly(ethyleneterephthalate) (PET). Moreover, almost no platelet adhesion was observed after 15?min perfusion in whole blood. Altogether, our results suggest that primary amine-rich plasma-polymerized coatings offer a promising stable and versatile method for PEG grafting in order to create nonfouling and nonthrombogenic surfaces and micropatterns. PMID:23509823

Thalla, Pradeep Kumar; Contreras-Garcia, Angel; Fadlallah, Hicham; Barrette, Jeremie; De Crescenzo, Gregory; Merhi, Yahye; Lerouge, Sophie

2013-01-01

283

Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide  

NASA Astrophysics Data System (ADS)

We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a `grafting from' technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures ( T g) than those of pristine PMMA.

Kumar, Mukesh; Chung, Jin Suk; Hur, Seung Hyun

2014-07-01

284

ION-PAIRING POLYMERIZATION  

Microsoft Academic Search

This account describes the development of a new type of polymerization catalysis termed ion-pairing polymerization (IPP). IPP utilizes compatible and dually active transition-metal cation–main-group anion ion pairs in which both the cation and the anion can independently catalyze the polymer chain growth in a single polymerization reaction. Furthermore, cations and anions of ion pairs can exhibit different stereoselectivity and growing

Eugene Y.-X. Chen

2009-01-01

285

Ferritin-Polymer Conjugates: Grafting Chemistry and Integration into Nanoscale Assemblies  

SciTech Connect

Controlled free radical polymerization chemistry is used to graft polymer chains to the corona of horse spleen ferritin (HSF) nanocages. Specifically, poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) and poly(PEG methacrylate) (polyPEGMA) chains are grafted onto the nanocages by atom transfer radical polymerization (ATRP), in which the molecular weight of the polymer grafts is controlled by the monomer-to-initiator feed ratio. PolyMPC and polyPEGMA-grafted ferritin show a generally suppressed inclusion into diblock copolymer films relative to native ferritin, and the polymer coating is seen to mask the ferritin nanocages from antibody recognition. The solubility of polyPEGMA-coated ferritin in organic solvents enables its processing with polystyrene-block-poly(ethylene oxide) copolymers, and selective integration into the PEO domains of microphase-separated copolymer structures.

Y Hu; D Samanta; S Parelkar; S Hong; Q Wang; T Russell; T Emrick

2011-12-31

286

The effect of ions on the enzymatically induced synthesis of lignin graft copolymers  

Microsoft Academic Search

The effect of different ions which are constituents of technical lignin sulfonates (LS) on chemo-enzymatic graft co-polymerization was determined. The application of the iron chelator desferrioxamine in the initial reaction mixture revealed that iron impurities of LS which catalyzed a Fenton-like reaction were crucial for the initiation of grafting, whereas calcium or chloride ions showed no such effect. The addition

Carsten Mai; Wiebke Schormann; Alois Hüttermann

2001-01-01

287

PDMS-based polyurethanes with MPEG grafts: synthesis, characterization and platelet adhesion study  

Microsoft Academic Search

Polyurethane (PU), based on poly(dimethyl siloxane) (PDMS) as a soft segment, with monomethoxy poly(ethylene glycol) (MPEG) grafted onto it, was synthesized as a new polymeric biomaterial for coating PDMS-based biomedical devices. Two different chain extenders, ethylene glycol (EG) and diethyl bis(hydroxymethyl) malonate (DBM), were used for the synthesis of PDMS-based PUs and then MPEG was grafted onto them by allophanate

Jae Hyung Park; Ki Dong Park; You Han Bae

1999-01-01

288

Toward living radical polymerization.  

PubMed

Radical polymerization is one of the most widely used processes for the commercial production of high-molecular-weight polymers. The main factors responsible for the preeminent position of radical polymerization are the ability to polymerize a wide array of monomers, tolerance of unprotected functionality in monomer and solvent, and compatibility with a variety of reaction conditions. Radical polymerization is simple to implement and inexpensive in relation to competitive technologies. However, conventional radical polymerization severely limits the degree of control that researchers can assert over molecular-weight distribution, copolymer composition, and macromolecular architecture. This Account focuses on nitroxide-mediated polymerization (NMP) and polymerization with reversible addition-fragmentation chain transfer (RAFT), two of the more successful approaches for controlling radical polymerization. These processes illustrate two distinct mechanisms for conferring living characteristics on radical polymerization: reversible deactivation (in NMP) and reversible or degenerate chain transfer (in RAFT). We devised NMP in the early 1980s and have exploited this method extensively for the synthesis of styrenic and acrylic polymers. The technique has undergone significant evolution since that time. New nitroxides have led to faster polymerization rates at lower temperatures. However, NMP is only applicable to a restricted range of monomers. RAFT was also developed at CSIRO and has proven both more robust and more versatile. It is applicable to the majority of monomers subject to radical polymerization, but the success of the polymerization depends upon the selection of the RAFT agent for the monomers and reaction conditions. We and other groups have proposed guidelines for selection, and the polymerization of most monomers can be well-controlled to provide minimal retardation and a high fraction of living chains by using one of just two RAFT agents. For example, a tertiary cyanoalkyl trithiocarbonate is suited to (meth)acrylate, (meth)acrylamide, and styrenic monomers, while a cyanomethyl xanthate or dithiocarbamate works with vinyl monomers, such as vinyl acetate or N-vinylpyrrolidone. With the appropriate choice of reagents and polymerization conditions, these reactions possess most of the attributes of living polymerization. We have used these methods in the synthesis of well-defined homo-, gradient, diblock, triblock, and star polymers and more complex architectures, including microgels and polymer brushes. Applications of these polymers include novel surfactants, dispersants, coatings and adhesives, biomaterials, membranes, drug-delivery media, electroactive materials, and other nanomaterials. PMID:18700787

Moad, Graeme; Rizzardo, Ezio; Thang, San H

2008-09-01

289

Polypeptoid Brushes by Surface-Initiated Polymerization of N-Substituted Glycine N-Carboxyanhydrides  

PubMed Central

Polypeptoid brushes were synthesized by surface-initiated polymerization of N-substituted glycine N-carboxyanhydrides (NNCAs) on self assembled amine monolayers. Using the presented grafting from approach, polypeptoid brush thicknesses of approx. 40 nm could be obtained as compared previously reported brush thicknesses of 4 nm. Moreover, hydrophilic, hydrophobic and amphiphilic polymer brushes were realized which are expected to have valuable applic-tions as non-fouling surfaces and as model or references systems for surface grafted polypeptides. PMID:23663172

Schneider, Maximilian; Fetsch, Corinna; Amin, Ihsan; Jordan, Rainer; Luxenhofer, Robert

2013-01-01

290

Chemically induced graft copolymerization of 2-hydroxyethyl methacrylate onto polyurethane surface for improving blood compatibility  

NASA Astrophysics Data System (ADS)

To improve hydrophilicity and blood compatibility properties of polyurethane (PU) film, we chemically induced graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of polyurethane film using benzoyl peroxide as an initiator. The effects of grafting temperature, grafting time, monomer and initiator concentrations on the grafting yields were studied. The maximum grafting yield value was obtained 0.0275 g/cm 2 for HEMA. Characterization of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements. ATR-FTIR data showed that HEMA was successfully grafted onto the PU films surface. Water contact angle measurement demonstrated the grafted films possessed a relatively hydrophilic surface. The blood compatibility of the grafted films was preliminarily evaluated by a platelet-rich plasma adhesion test and hemolysis test. The results of platelet adhesion experiment showed that polyurethane grafted polymerization with monomer of 2-hydroxyethyl methacrylate had good blood compatibility featured by the low platelet adhesion. Hemolysis rate of the PU-g-PHEMA films was dramatically decreased than the ungrafted PU films. This kind of new biomaterials grafted with HEMA monomers might have a potential usage for biomedical applications.

He, Chunli; Wang, Miao; Cai, Xianmei; Huang, Xiaobo; Li, Li; Zhu, Haomiao; Shen, Jian; Yuan, Jiang

2011-11-01

291

Calcium carbonate crystallization in the presence of modified polysaccharides and linear polymeric additives  

NASA Astrophysics Data System (ADS)

Crystallization of calcium carbonate was performed in the presence of grafted polysaccharides, polyacrylamide (PAM) and polyacrylic acid (PAA). The grafted polysaccharides gave crystal morphologies that were different from the unmodified polysaccharides but similar to the ones given by homopolymers of the grafted chains. PAM-grafted ?-cellulose gave rectangular platelets that aggregated to form 'spherical' crystals on the surface of the fiber, whereas PAA grafted ?-cellulose gave spherical crystals on the surface of the fiber. X-ray diffraction (XRD) spectroscopy showed that PAM-grafted ?-cellulose, PAM as well as the control (no polymeric additive) gave calcite crystals at both 25 and 80 °C. However, the PAA-grafted ?-cellulose and PAA homopolymer gave calcite and vaterite crystals at 25 °C with calcite and aragonite crystals along with traces of vaterite being formed at 80 °C. The fiber surface coverage by these crystals was more on the acrylic- and acrylamide-grafted cellulose than on the ungrafted ?-cellulose. The evolution of CaCO 3 polymorphs as well as crystal morphology in PAA-grafted starch was similar to that of PAA-grafted ?-cellulose at the two temperatures employed.

Matahwa, H.; Ramiah, V.; Sanderson, R. D.

2008-10-01

292

Halley's polymeric organic molecules  

NASA Astrophysics Data System (ADS)

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets.

Huebner, W. F.; Boice, D. C.; Korth, A.

293

Thermodynamics of Polymerization. I  

Microsoft Academic Search

I. THE CHILING TEMPERATURE CONCEPT A. Thermodynamic Approach The Gibbs free energy of a system at temperature T is defined as were H is the enthalpy and S the entropy of the system. The free energy change for any polymerization will be, therefore, When the polymer has a lower free energy than the initial monomer, a polymerization can occur spontaneously,

Hideo Sawada

1969-01-01

294

Phase Behavior and Significantly Enhanced Toughness in Polylactide Graft Copolymers  

NASA Astrophysics Data System (ADS)

Polylactide (PLA), a biodegradable polyester derived from plant sugars, is commercially available and used in a variety of applications ranging from serviceware to resorbable sutures. One limitation to diversifying the applications of the material is its inherent brittleness. Graft copolymers containing PLA arms and a rubbery aliphatic polymer backbone were synthesized by a combination of ring-opening metathesis and ring-opening transesterification polymerizations. The high degree of incompatibility between the arms and backbone resulted in microphase separation of the graft copolymer at increasingly low fractions of the backbone polymer, as evidenced by small-angle x-ray scattering. In graft copolymers with a rubbery content of only 5 wt percent, the tensile strain at break was observed to be as high as twenty times that of neat PLA. Studies are underway to provide insight into the critical polymer molecular parameters for enhanced toughness and the deformation mechanisms.

Robertson, Megan; Theryo, Grayce; Jing, Feng; Hillmyer, Marc

2011-03-01

295

Synthetic bone graft substitutes.  

PubMed

Replacement of extensive local bone loss is a significant clinical challenge. There are a variety of techniques available to the surgeon to manage this problem, each with their own advantages and disadvantages. It is well known that there is morbidity associated with harvesting of autogenous bone graft and limitations in the quantity of bone available. Alternatively allografts have been reported to have a significant incidence of postoperative infection and fracture as well as the potential risk of disease transmission. During the past 30 years a variety of synthetic bone graft substitutes has been developed with the aim to minimize these complications. The benefits of synthetic grafts include availability, sterility and reduced morbidity. The present article examines the relevance of synthetic bone graft substitutes, their mechanical properties and clinical application. PMID:11409021

Moore, W R; Graves, S E; Bain, G I

2001-06-01

296

Effects of solvent polarity on mutual styrene grafting onto polypropylene by electron beam irradiation  

NASA Astrophysics Data System (ADS)

Radiation induced mutual grafting of styrene onto polypropylene has been carried using several grafting solutions with different organic solvents and polarity levels. In the mixture of styrene and protic polar solvents high grafting yields were obtained. This behavior suggests that grafting process does not have dependence on swelling of the substrate, something that is expected when a non-polar substrate and a non-polar media are in contact. In this case, the grafting yield may be related to the free radical generation at protic polar solvent; these reactive specimens start the reaction on substrate surface to allow the accessibility of monomer species to active sites. Some reaction mechanisms are proposed.

Moura, E.; Manzoli, J. E.; Geraldo, A. B. C.

2012-09-01

297

Controlled graft copolymerization of lactic acid onto starch in a supercritical carbon dioxide medium.  

PubMed

This work presents a new approach for the synthesis of a starch-g-poly L-lactic acid (St-g-PLA) copolymer via the graft copolymerization of LA onto starch using stannous 2-ethyl hexanoate (Sn(Oct)2) as a catalyst in a supercritical carbon dioxide (scCO2) medium. The effects of several process parameters, including the pressure, temperature, scCO2 flow rate and reaction time, on the polymerization yield and grafting degree were studied. Amorphous graft St-g-PLA copolymers with increased thermal stability and processability were produced with a high efficiency. The maximum grafting degree (i.e., 52% PLA) was achieved with the following reaction conditions: 6h, 100°C, 200bar and a 1:3 (w/w) ratio of St/LA. It was concluded that these low cost biobased graft biopolymers are potential candidates for several environment-friendly applications. PMID:25263875

Salimi, Kouroush; Yilmaz, Mehmet; Rzayev, Zakir M O; Piskin, Erhan

2014-12-19

298

Treatment of oil in water emulsions by ceramic-supported polymeric membranes  

SciTech Connect

A novel membrane was developed by growing polymer chains from the surface of a porous ceramic support, resulting in a composite membrane which combines the mechanical properties of the inorganic membrane with the selective interactions of the polymer. The configuration of the grafted polymer brush layer is determined by solvent-polymer interactions, with a hydrophilic polymer being stretched away from the surface by aqueous solutions and collapsed against the surface by organic solvents. This behavior of the grafted chains provides Ceramic-Supported Polymeric (CSP) membranes with unique properties for certain water treatment applications. One application envisioned for these CSP membranes, in which the selectivity is influenced by interactions between the solvent and the grafted polymer, is the cross-flow filtration of an oil-in-water emulsion. In this case, a hydrophilic grafted Polyvinylpyrrolidone (PVP) brush layer expanded into the pore volume due to the affinity of the polymer for water. These extended grafted chains preferentially allow the passage of water over oil, producing a permeate stream with a lower total organic carbon content compared to an unmodified membrane. Another advantage of the CSP membrane is in reducing permeate flux decline believed to be caused by the adsorption of oil onto the membrane surface. For the PVP-modified CSP membrane, the grafted polymer alters the membrane surface character from hydrophobic to hydrophilic, reducing the tendency for oil adsorption. This phenomenon was demonstrated by comparison of permeate flow rate behavior for both unmodified and graft polymerized (CSP) membranes.

Castro, R.P.; Cohen, Y.; Monbouquette, H.G. [Univ. of California, Los Angeles, CA (United States). Dept. of Chemical Engineering

1994-12-31

299

Multiphase Polymeric Materials  

NSDL National Science Digital Library

Developed by a group of PhD students at the University of Southern Mississippi, the Multiphase Polymeric Materials Website presents both general information about composites and current research on multiphase polymeric materials, including information about blends, coatings, and nanocomposites. As the newest addition to Macrogalleria (described in the March 31, 1999 Scout Report for Science & Engineering), the Multiphase Polymeric Materials Website includes information on Composites in General, Composites, Characterization and Analysis, and Application. Most useful to researchers, the Application section introduces the relationship between polymer composites and component level electronics with examples such as PCB Construction, Encapsulation of Integrated Circuits, and Non-Conductive Adhesives.

300

synthesis of novel four armed PE-PCL grafted superparamagnetic and biocompatible nanoparticles.  

PubMed

Novel biocompatible polymer immobilized superparamagnetic nanoparticles (MNP) are prepared by grafting four armed pentaerythritol poly(?-polycaprolactone) (PE-PCL) onto silane modified MNP. The MNPs are synthesized by hydrothermal process and its modification using (3-aminopropyl)trimethoxysilane (TMAS) coating is done by the sol-gel technique. The pentaerythritol (PE) initiated ring-opening polymerization (ROP) is carried out to prepare four armed PE-PCL. The reaction is shown to follow first order kinetics. The structure of PE-PCL is confirmed by NMR spectrum and MALDI-TOF analysis. The in situ grafting of PE-PCL onto modified MNP has been carried out by using 4,4'-methylenediphenyl diisocyanate (MDI) as an intermediate linker. The grafting density as determined by TGA analysis has been found to be significantly higher than previously reported linear PCL grafted MNPs in the literature. This leads to uniform dispersion of grafted MNPs which still is a challenging task in contemporary research. The effective dispersion of MNP into PE-PCL matrix is analyzed by HRTEM. The saturation magnetization of the PE-PCL grafted MNPs is significantly high and this can be tailored further by varying the grafting density. The biocompatibility of polymer grafted nanoparticles is confirmed by MTT assay using HeLa cell line. The superparamagnetic and biocompatible novel PE-PCL grafted MNP so prepared would have manifold potential applications including in therapy and targeted drug delivery. PMID:24041315

Panja, Sudipta; Saha, Biswajit; Ghosh, S K; Chattopadhyay, Santanu

2013-10-01

301

Structure of polymer layers grafted to nanoparticles in silica-polystyrene nanocomposites  

E-print Network

The structural features of polystyrene brushes grafted on spherical silica nanoparticles immersed in polystyrene are investigated by means of a Monte Carlo methodology based on polymer mean field theory. The nanoparticle radii (either 8 nm or 13 nm) are held constant, while the grafting density and the lengths of grafted and matrix chains are varied systematically in a series of simulations. The primary objective of this work is to simulate realistic nanocomposite systems of specific chemistry at experimentally accessible length scales and study the structure and scaling of the grafted brush. The profiles of polymer density around the particles are examined; based on them, the brush thickness of grafted chains is estimated and its scaling behavior is compared against theoretical models and experimental findings. Then, neutron scattering spectra are predicted both from single grafted chains and from the entire grafted corona. It is found that increasing both the grafting density and the grafted chain molar mass drastically alters the brush dimensions, affecting the wetting behavior of the polymeric brush. On the contrary, especially for particles dispersed in high molecular weight matrix, variation of the matrix chain length causes an almost imperceptible change of the density around the particle surface.

Georgios G. Vogiatzis; Doros N. Theodorou

2014-01-16

302

Metallocene Catalysts for Ethylene Polymerization  

Microsoft Academic Search

Metallocene catalysts are the latest addition to the olefin polymerization catalyst family. It has been demonstrated that metallocene catalyst can polymerize olefins at high activities. Some chiral metallocenes are also capable of stereospecific polymerization where isotactic and syndiotactic polymers can be produced. Although it was proven that metallocene catalysts can polymerize ethylene in the late fifties, it took more than

Syriac J. Palackal; Atieh Abu Raqabah

303

Nanoconfinement Effect on Polymerization  

NASA Astrophysics Data System (ADS)

Ring-opening metathesis polymerization of endo-dicyclopentadidene (DCPD) with second generation Grubbs catalyst is carried out under nanoscale constraint. Differential scanning calorimetry is used to study the polymerization reaction both in the bulk and in the nanopores of controlled pore glass as a function of heating rate; the Tg of the resulting reaction product is also determined. In 110 nm-diameter pores, DCPD undergoes incomplete polymerization followed by the reverse Diels-Alder reaction to form pentadiene. Decreasing the heating rate shifts both reactions towards lower temperatures but does not avert the side reaction. In the bulk unconfined case, the reverse Diels-Alder reaction only occurs in the absence of catalyst. The glass transition temperature of the nanoconfined polymerization product is 164 C, approximately 20 C higher than the polymer prepared under bulk conditions. Reaction kinetics in bulk and nanoconfined cases will also be discussed.

Vaddey, Maitri; Simon, Sindee

2011-03-01

304

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Two of the major environmental hazards in the Geosynchronous Earth Orbit (GEO) are energetic charged particles and ultraviolet radiation. The charged particles, electrons and protons, range in energy from 0.1 to 4 MeV and each have a flux of 10 to the 8th sq cm/sec. Over a 30 year lifetime, materials in the GEO will have an absorbed dose from this radiation of 10 to the 10th rads. The ultraviolet radiation comes uninhibited from the sun with an irradiance of 1.4 kw/sq m. Radiation is known to initiate chain sission and crosslinking in polymeric materials, both of which affect their structural properties. The 30-year dose level from the combined radiation in the GEO exceeds the threshold for measurable damage in most polymer systems studied. Of further concern is possible synergistic effects from the simultaneous irradiation with charged particles and ultraviolet radiation. Most studies on radiation effects on polymeric materials use either electrons or ultraviolet radiation alone, or in a sequential combination.

Kiefer, Richard L.; Orwoll, Robert A.

1988-01-01

305

PREFACE: IUMRS-ICA 2008 Symposium, Sessions 'X. Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' and 'Y. Frontier of Polymeric Nano-Soft-Materials - Precision Polymer Synthesis, Self-assembling and Their Functionalization'  

NASA Astrophysics Data System (ADS)

Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science (Symposium X of IUMRS-ICA2008) Toshiji Kanaya, Kohji Tashiro, Kazuo Sakura Keiji Tanaka, Sono Sasaki, Naoya Torikai, Moonhor Ree, Kookheon Char, Charles C Han, Atsushi Takahara This volume contains peer-reviewed invited and contributed papers that were presented in Symposium X 'Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' at the IUMRS International Conference in Asia 2008 (IUMRS-ICA 2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Structure analyses of soft materials based on synchrotron radiation (SR) and neutron beam have been developed steadily. Small-angle scattering and wide-angle diffraction techniques clarified the higher-order structure as well as time dependence of structure development such as crystallization and microphase-separation. On the other hand, reflectivity, grazing-incidence scattering and diffraction techniques revealed the surface and interface structural features of soft materials. From the viewpoint of strong interests on the development of SR and neutron beam techniques for soft materials, the objective of this symposium is to provide an interdisciplinary forum for the discussion of recent advances in research, development, and applications of SR and neutron beams to soft matter science. In this symposium, 21 oral papers containing 16 invited papers and 14 poster papers from China, India, Korea, Taiwan, and Japan were presented during the three-day symposium. As a result of the review of poster and oral presentations of young scientists by symposium chairs, Dr Kummetha Raghunatha Reddy (Toyota Technological Institute) received the IUMRS-ICA 2008 Young Researcher Award. We are grateful to all invited speakers and many participants for valuable contributions and active discussions. Organizing committee of Symposium (IUMRS-ICA 2008) Professor Toshiji Kanaya (Kyoto University) Professor Kohji Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y 'Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization' at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. 'Polymeric nano-soft-materials' are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y aimed to provide recent advances in polymer synthesis, self-assembling processes and morpholog

Takahara, Atsushi; Kawahara, Seiichi

2009-09-01

306

Long-term hip simulator testing of the artificial hip joint bearing surface grafted with biocompatible phospholipid polymer.  

PubMed

To prevent periprosthetic osteolysis and subsequent aseptic loosening of artificial hip joints, we recently developed a novel acetabular highly cross-linked polyethylene (CLPE) liner with graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) on its surface. We investigated the wear resistance of the poly(MPC) (PMPC)-grafted CLPE liner during 20 million cycles in a hip joint simulator. We extended the simulator test of one liner to 70 million cycles to investigate the long-term durability of the grafting. Gravimetric, surface, and wear particle analyses revealed that PMPC grafting onto the CLPE liner surface markedly decreased the production of wear particles and showed that the effect of PMPC grafting was maintained through 70 million cycles. We believe that PMPC grafting can significantly improve the wear resistance of artificial hip joints. PMID:24249706

Moro, Toru; Takatori, Yoshio; Kyomoto, Masayuki; Ishihara, Kazuhiko; Hashimoto, Masami; Ito, Hideya; Tanaka, Takeyuki; Oshima, Hirofumi; Tanaka, Shigeyuki; Kawaguchi, Hiroshi

2014-03-01

307

Inclusion polymerization of isoprene in deoxycholic acid  

NASA Astrophysics Data System (ADS)

The radiation-induced polymerization of isoprene was made on its inclusion (or clathrate) complex with deoxycholic acid (DOCA) at 150 and 300 kGy. The microstructure of the resulting polyisoprene (PIP) was studied by FTIR spectroscopy and found fully comparable to that of PIP prepared by emulsion polymerization by a free radical initiator. Thus, the 1,4-trans content was found to be 48% and that of 1,4-cis units was 28% of the polymer structure; the remaining are being 1,2 and 3,4 units. The PIP irregular microstructure was justified in terms of monomer dynamics inside the DOCA channels. PIP from inclusion polymerization is fully amorphous as studied by differential thermal analysis (DTA) in comparison to an authentic sample of trans-1,4-polyisoprene, which instead has a crystalline melting point of 71.5 °C. The inclusion complex of PIP with DOCA (PIP@DOCA) shows a DTA melting point of 194.4 °C, 12.4 °C higher than the melting point of pure DOCA. PIP isolated from inclusion polymerization from DOCA and its complex PIP@DOCA was studied also by thermogravimetry (TGA) and differential thermogravimetry (DTG). Isoprene does not form inclusion complexes with urea and thiourea. When irradiated with these two compounds it produces an oily PIP oligomer whose microstructure was found by FTIR spectroscopy analogous to that of PIP prepared by emulsion polymerization by a free radical initiator.

Cataldo, Franco; Ragni, Pietro; Rosati, Aldo; Ursini, Ornella

2009-05-01

308

New graft copolymers of hyaluronic acid and polylactic acid: Synthesis and characterization  

Microsoft Academic Search

New graft copolymers have been synthesized, using hyaluronic acid (HA) as a hydrophilic backbone and polylactic acid (PLA) as an aliphatic polyester in order to obtain new polymeric derivatives of HA able to hydrophobically associate in an aqueous medium. Hyaluronic acid with low molecular weight was made soluble in organic solvent by transformation to its tetrabutylammonium (TBA) salt. Using the

Fabio Salvatore Palumbo; Giovanna Pitarresi; Delia Mandracchia; Giuseppe Tripodo; Gaetano Giammona

2006-01-01

309

Dacron Graft Aneurysm Treated by Endovascular Stent-Graft  

Microsoft Academic Search

A 72-year old man who underwent aorto-bifemoral bypass with insertion of a Dacron graft 18 years previously presented with an aneurysm in the left limb of his graft. Angiography also demonstrated a bilateral occlusion of the popliteal arteries. Computed tomography (CT) angiography was performed and showed a localized dilation of 3 cm in the left limb of the graft, which

Amos Ofer; Samy Nitecki; Aaron Hoffman; Ahuva Engel

2001-01-01

310

Surface Modification of Multiwalled Carbon Nanotubes via Nitroxide-Mediated Radical Polymerization  

E-print Network

)-grafted multiwalled carbon nano- tubes (MWNT­PS-b-P4VPs). In contrast to unmodified MWNTs, MWNT­PSs had rel- atively carbon nanotubes (MWNTs), polymer modification leaves less destruction of tube structure while achievingSurface Modification of Multiwalled Carbon Nanotubes via Nitroxide-Mediated Radical Polymerization

Wan, Xin-hua

311

Grafting of Hydroxyethyl Methacrylate onto Gelatin  

Microsoft Academic Search

Gelatin was graft copolymerized with poly (hydroxyethyl methacrylate) (HEMA) using potassium peroxydisulphate in aqueous medium. Effect of temperature, initiator, monomer and backbone concentrations were studied. The percent grafting was found to increase initially and then decrease in all the cases except with variation of backbone concentration. The rate of grafting, grafting efficiency and percent grafting were calculated. The grafting results

M. Sivakumar; P. Rajalingam; Ganga Radhakrishnan

1991-01-01

312

Tailoring the properties of thermoplastic starch by blending with cinnamyl alcohol and radiation processing: An insight into the competitive grafting and scission reactions  

NASA Astrophysics Data System (ADS)

The present paper focuses on the effects of electron beam (EB) irradiation on thermoplastic materials based on destructurized starch including glycerol and water as plasticizers to assess the potentiality of cinnamyl alcohol as reactive additive capable of counterbalancing the degradation of the polysaccharide by inducing interchain covalent linkages. The tensile properties at break of test specimens of controlled composition submitted to EB irradiation at doses ranging from 50 to 200 kGy revealed the presence of competitive chain scission and bridging in samples containing cinnamyl alcohol at a relative concentration of 2.5% with regard to dry starch. The occurrence of crosslinking under particular conditions was evidenced by gel fraction measurements. The treatment under radiation was also applied to model blends including maltodextrin as a model for starch and the other ingredients to gain an insight into the radiation induced mechanisms at the molecular level. The presence of cinnamyl alcohol is found to limit degradation. Size exclusion chromatography and gel fraction allowed to monitor the effects and confirmed unambiguously the attachment of UV-absorbing chromophores onto the maltodextrin main chain. The combination of the obtained results demonstrates the possibility of altering in a favorable way the tensile properties of plasticized starch by applying high energy radiation to properly formulated blends including aromatic compounds like cinnamyl alcohol.

Khandal, Dhriti; Mikus, Pierre-Yves; Dole, Patrice; Bliard, Christophe; Soulestin, Jérémie; Lacrampe, Marie-France; Baumberger, Stéphanie; Coqueret, Xavier

2012-08-01

313

Accompanying of parameters of color, gloss and hardness on polymeric films coated with pigmented inks cured by different radiation doses of ultraviolet light  

NASA Astrophysics Data System (ADS)

In the search for alternatives to traditional paint systems solvent-based, the curing process of polymer coatings by ultraviolet light (UV) has been widely studied and discussed, especially because of their high content of solids and null emission of VOC. In UV-curing technology, organic solvents are replaced by reactive diluents, such as monomers. This paper aims to investigate variations on color, gloss and hardness of print inks cured by different UV radiation doses. The ratio pigment/clear coating was kept constant. The clear coating presented higher average values for König hardness than pigmented ones, indicating that UV-light absorption has been reduced by the presence of pigments. Besides, they have indicated a slight variation in function of cure degree for the studied radiation doses range. The gloss loss related to UV light exposition allows inferring that some degradation occurred at the surface of print ink films.

Bardi, Marcelo Augusto Gonçalves; Machado, Luci Diva Brocardo

2012-09-01

314

Preparation and adsorption of bovine serum albumin-imprinted polyacrylamide hydrogel membrane grafted on non-woven polypropylene.  

PubMed

Bovine serum albumin (BSA) imprinted polypropylene (PP) fiber-grafted polyacrylamide (PAM) hydrogel membrane (PP-g-PAM MIP) was prepared using non-woven PP fiber as matrix, BSA as template molecule, and acrylamide (AM) as functional monomer via UV radiation-reduced polymerization in an aqueous phase. SEM, FT-IR, DSC and TG were used to characterize the PP grafted PAM hydrogel. Influence factors on the adsorption capacity of PP-g-PAM MIP were investigated, such as monomer concentration, cross-linker concentration, template molecule amount and pH values in BSA solution. The adsorption and recognition properties of PP-g-PAM MIP were evaluated and the results showed that the PP-g-PAM MIP exhibited an obvious improvement in terms of adsorption capacity for BSA as compared with non-imprinted ones. PP-g-PAM MIPs could recognize the template protein using Lys, Ova, BHb, and Glo as control proteins, and the selectivity factor (?) was above 2.0. The imprinting efficiency of PP-g-PAM MIP tended to be stable after three cycles and maintained 76% of the initial value of the imprinting efficiency even after five repetitions, which was more excellent than that of PAM microsphere. The PP-g-PAM MIP is low cost and easy to be prepared, which would show its potential applications in the fields of extracting and testing required proteins from cells or particulate samples. PMID:24607136

Zhao, Kongyin; Lin, Beibei; Cui, Wenkui; Feng, Lingzhi; Chen, Tian; Wei, Junfu

2014-04-01

315

Bone Grafts in Craniofacial Surgery  

PubMed Central

Reconstruction of cranial and maxillofacial defects is a challenging task. The standard reconstruction method has been bone grafting. In this review, we shall describe the biological principles of bone graft healing, as pertinent to craniofacial reconstruction. Different types and sources of bone grafts will be discussed, as well as new methods of bone defect reconstruction. PMID:22110806

Elsalanty, Mohammed E.; Genecov, David G.

2009-01-01

316

Entropic forces generated by grafted semiflexible polymers  

E-print Network

The entropic force exerted by the Brownian fluctuations of a grafted semiflexible polymer upon a rigid smooth wall are calculated both analytically and by Monte Carlo simulations. Such forces are thought to play an important role for several cellular phenomena, in particular, the physics of actin-polymerization-driven cell motility and movement of bacteria like Listeria. In the stiff limit, where the persistence length of the polymer is larger than its contour length, we find that the entropic force shows scaling behavior. We identify the characteristic length scales and the explicit form of the scaling functions. In certain asymptotic regimes we give simple analytical expressions which describe the full results to a very high numerical accuracy. Depending on the constraints imposed on the transverse fluctuations of the filament there are characteristic differences in the functional form of the entropic forces; in a two-dimensional geometry the entropic force exhibits a marked peak.

Azam Gholami; Jan Wilhelm; Erwin Frey

2006-03-05

317

Grafted semiconductor optoelectronics  

NASA Astrophysics Data System (ADS)

A description is given of the use of epitaxial lift-off (ELO) for optoelectronics. With ELO, a high-quality GaAs-AlGaAs or InP0.53Ga0.47As film is removed from its growth substrate by selective etching and then grafted to a new substrate, through van der Waals forces, where it is used for device fabrication. The semiconductor devices are made completely on the new substrate so they can be photolithographically aligned and batch processed. Details of the ELO procedure and subsequent grafted device fabrication are presented. The authors establish that the grafted film is in optical contact with the new substrate, and they describe devices, such as an LiNbO3 waveguide detector and a GaAs-glass waveguide grating coupler, which are based on this coupling. Besides photodetectors, grafted GaAs field-effect transistors, another important component for optoelectronics, that show dc and RF performances similar to those of devices made on the growth wafer are also described.

Chan, Winston K.; Yi-Yan, Alfredo; Gmitter, Thomas J.

1991-03-01

318

Rapid fabrication of polymeric micro lenses for optical fiber trapping and beam shaping  

NASA Astrophysics Data System (ADS)

This work reports a new type of optical fiber tweezers based on polymeric micro-lenses. The lenses are achieved by means of an economical and fast fabrication process, using an in-fiber photo-polymerization technique. The polymerization radiation is guided towards the fiber tip creating a polymeric waveguide. The method allows tailoring the geometry of the tip by adjusting the fabrication parameters. Furthermore, more complex shapes can be fabricated by exploring modal effects at the polymerization/trapping wavelengths, which can be used for different applications such as trapping, beam shaping and patterned illumination.

Rodrigues Ribeiro, R. S.; Queirós, R. B.; Ecoffet, C.; Soppera, O.; Oliva, A.; Guerreiro, A.; Jorge, P. A. S.

2014-09-01

319

Injectable PolyHIPEs as High Porosity Bone Grafts  

PubMed Central

Polymerization of high internal phase emulsions (polyHIPEs) is a relatively new method for the production of high porosity scaffolds. The tunable architecture of these polyHIPE foams make them attractive candidates for tissue engineered bone grafts. Previously studied polyHIPE systems require either toxic diluents or high cure temperatures which prohibit their use as an injectable bone graft. In contrast, we have developed an injectable polyHIPE that cures at physiological temperatures to a rigid, high-porosity foam. First, a biodegradable macromer, propylene fumarate dimethacrylate (PFDMA), was synthesized that has appropriate viscosity and hydrophobicity for emulsification. The process of surfactant selection is detailed with particular focus on the key structural features of both polymer (log P values, hydrogen bond acceptor sites) and surfactant (HLB values, hydrogen bond donor sites) that enable stable HIPE formation. Incubation of HIPEs at 37°C was used to initiate radical crosslinking of the unsaturated double bond of the methacrylate groups to polymerize the continuous phase and lock in the emulsion geometry. The resulting polyHIPEs exhibited ~75% porosity, pore sizes ranging from 4 to 29 ?m, and an average compressive modulus and strength of 33 and 5 MPa, respectively. These findings highlight the great potential of these scaffolds as injectable, tissue engineered bone grafts. PMID:21861465

Moglia, Robert S.; Holm, Jennifer L.; Sears, Nicholas A.; Wilson, Caitlin J.; Harrison, Dawn M.; Cosgriff-Hernandez, Elizabeth

2011-01-01

320

Injectable polyHIPEs as high-porosity bone grafts.  

PubMed

Polymerization of high internal phase emulsions (polyHIPEs) is a relatively new method for the production of high-porosity scaffolds. The tunable architecture of these polyHIPE foams makes them attractive candidates for tissue engineered bone grafts. Previously studied polyHIPE systems require either toxic diluents or high cure temperatures which prohibit their use as an injectable bone graft. In contrast, we have developed an injectable polyHIPE that cures at physiological temperatures to a rigid, high-porosity foam. First, a biodegradable macromer, propylene fumarate dimethacrylate (PFDMA), was synthesized that has appropriate viscosity and hydrophobicity for emulsification. The process of surfactant selection is detailed with particular focus on the key structural features of both polymer (logP values, hydrogen bond acceptor sites) and surfactant (HLB values, hydrogen bond donor sites) that enable stable HIPE formation. Incubation of HIPEs at 37 °C was used to initiate radical cross-linking of the unsaturated double bond of the methacrylate groups to polymerize the continuous phase and lock in the emulsion geometry. The resulting polyHIPEs exhibited ~75% porosity, pore sizes ranging from 4 to 29 ?m, and an average compressive modulus and strength of 33 and 5 MPa, respectively. These findings highlight the great potential of these scaffolds as injectable, tissue engineered bone grafts. PMID:21861465

Moglia, Robert S; Holm, Jennifer L; Sears, Nicholas A; Wilson, Caitlin J; Harrison, Dawn M; Cosgriff-Hernandez, Elizabeth

2011-10-10

321

Silicon tetrachloride plasma induced grafting for starch-based composites  

NASA Astrophysics Data System (ADS)

Non-modified virgin starch is seldom used directly in industrial applications. Instead, it is often physically and/or chemically modified to achieve certain enhanced properties. For many of the non-food applications, these modifications involve changing its hydrophilicity to create hydrophobic starch. In this study, the hydrophobic starch was produced through silicon tetrachloride (SiCl4) plasma induced graft polymerization, so that it could be used as a renewable and biodegradable component of, or substitute for, the petrochemical-based plastics. It was suggested that this starch graft-copolymer might be used as reinforcing components in silicone-rubber materials for starch-based composites. To make this starch graft-copolymer, the ethyl ether-extracted starch powders were surface functionalized by SiCl4 plasma using a 13.56 MHz radio frequency rotating plasma reactor and subsequently stabilized by either ethylene diamine or dichlorodimethylsilane (DCDMS). The functionalized starch was then graft-polymerized with DCDMS to form polydimethylsiloxane (PDMS) layers around the starch granules. The presence of this PDMS layer was demonstrated by electron spectroscopy for chemical analysis (ESCA/XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), gas chromatography-mass spectroscopy (GC-MS), thermo gravimetry/differential thermal analysis (TG/DTA), and other analyses. It was shown that the surface morphology, thermal properties, swelling characteristic, and hydrophilicity of starch were all changed due to the existence of this protective hydrophobic PDMS layer. Several different procedures to carry out the functionalization and graft polymerization steps were evaluated to improve the effectiveness of the reactions and to prevent the samples from being hydrolyzed by the grafting byproduct HCl. Actinometry, GC-MS, and residual gas analyzer (RGA) were used to investigate the mechanisms of the SiCl4 discharge and to optimize the plasma modification. These plasma diagnostic results showed that, to achieve better plasma modification, higher plasma power and lower SiCl4 vapor pressure would be needed; however, it was found that the efficiency of the modification peaked at a certain point of plasma treatment time (˜10 minutes) and there was not much subsequent improvement with prolonged plasma treatment.

Ma, Yonghui C.

322

One-pot synthesis of brush-like polymers via integrated ring-opening metathesis polymerization and polymerization of amino acid N-carboxyanhydrides.  

PubMed

We report here the integration of ring-opening metathesis polymerization (ROMP) and ring-opening polymerization of the amino acid N-carboxyanhydride (NCA) to allow facile synthesis of brush-like polymers containing polypeptide as the brush side chains. ROMP of N-trimethylsilyl norbornenes rendered the preparation of poly(norbornene)s bearing pendant N-TMS groups. With no need to purify the resulting polymers, such macromolecular initiators could subsequently initiate controlled NCA polymerizations. Brush-like poly(norbornene)s with grafted polypeptides or block copolypeptides were readily obtained with controlled molecular weights and narrow molecular weight distributions. Because numerous ROMP and NCA monomers are widely available, this novel polymerization technique will allow easy access to numerous brush-like hybrid macromolecules with unprecedented properties and broad applications. PMID:19725499

Lu, Hua; Wang, Jing; Lin, Yao; Cheng, Jianjun

2009-09-30

323

Polystyrene latex by dispersion polymerization: real time SAXS measurements  

Microsoft Academic Search

The purpose of this work was the characterization of polystyrene and poly(styrene-co-Boc-aminostyrene) latex particles obtained by dispersion polymerization as a function of reaction time. Small angle scattering of X-rays (SAXS) using synchrotron radiation was the main technique used to describe the system, by means of real time experiments (in situ) and in samples prepared from extracts of the polymerization reaction

Vera L. Covolan; Pedro L. O. Volpe; Tomás S. Plivelic; Iris L. Torriani

2002-01-01

324

Assembly of Highly Grafted Polymer Nanoparticle Hybrids  

NASA Astrophysics Data System (ADS)

Spherical nanoparticles of silica grafted with a dense brush of low polydispersity polymers prepared by living radical polymerization are shown to form ordered crystalline structures with cubic symmetry. The minimum distance between nanoparticle surfaces, a good measure of the end-to-end distance of the tethered polymers, scales as the square-root of the molecular weight of the polymer chains. The blending of the grafted nanoparticles with homopolymers of matched and mismatched molecular weights indicates that the crystalline order persists even with high amounts of homopolymer added and for such diluted systems with as little as 0.007 vol fraction silica. On the other hand, the introduction of an incompatible block copolymer on the spherical nanoparticle or the introduction of slight asymmetry in the shape of the nanoparticle, leads to significant perturbation of the local ordering. However in the presence of external fields such as shear these nano-hybrids can develop into highly anisotropic mesostructures. Understanding the basis for the disruption in local ordering and the ability to create anisotropic mesostructures is the topic of this presentation.

Krishnamoorti, Ramanan

2012-02-01

325

Preparation of poly(ether ether ketone)-based polymer electrolytes for fuel cell membranes using grafting technique  

NASA Astrophysics Data System (ADS)

Poly(ether ether ketone) (PEEK)-based polymer electrolyte membranes (PEMs) was successfully prepared by radiation grafting of a styrene monomer into PEEK films and the consequent selective sulfonation of the grafting chains in the film state. Using milder sulfonation, the sulfonation reactions proceeded at the grafted chains in preference to the phenylene rings of PEEK main chains; as a result, the grafted films could successfully transform to a PEM with conductivity of more than 0.1 S/cm. The ion exchange capacity (IEC) and conductivity of the grafted PEEK electrolyte membranes were controlled to the ranges of 1.2-2.9 mmol/g and 0.03-0.18 S/cm by changing the grafting degree. It should be noted that this is the first example of directly transforming super-engineering plastic films into a PEM using radiation grafting.

Hasegawa, Shin; Suzuki, Yasuyuki; Maekawa, Yasunari

2008-05-01

326

Studies in reactive extrusion processing of biodegradable polymeric materials  

NASA Astrophysics Data System (ADS)

Various reaction chemistries such as Polymerization, Polymer cross-linking and Reactive grafting were investigated in twin-screw extruders. Poly (1,4-dioxan-2-one) (PPDX) was manufactured in melt by the continuous polymerization of 1,4-dioxan-2-one (PDX) monomer in a twin-screw extruder using Aluminum tri-sec butoxide (ATSB) initiator. Good and accurate control over molecular weight was obtained by controlling the ratio of monomer to initiator. A screw configuration consisting of only conveying elements was used for the polymerization. The polymerization reaction was characterized by a monomer-polymer dynamic equilibrium, above the melting temperature of the polymer, limiting the equilibrium conversion to 78-percent. Near complete (˜100-percent) conversion was obtained on co-polymerizing PDX monomer with a few mol-percent (around 8-percent) Caprolactone (CL) monomer in a twin-screw extruder using ATSB initiator. The co-polymers exhibited improved thermal stability with reduction in glass transition temperature. The extruder was modeled as an Axial Dispersed Plug Flow Reactor for the polymerization of CL monomer using Residence Time Distribution (RTD) Analysis. The model provided a good fit to the experimental RTD and conversion data. Aliphatic and aliphatic-aromatic co-polyesters, namely Polycaprolactone (PCL) and Poly butylenes (adipate-co-terephthalate) (Ecoflex) were cross-linked in a twin-screw extruder using radical initiator to form micro-gel reinforced biodegradable polyesters. Cross-linked Ecoflex was further extrusion blended with talc to form blends suitable to be blown into films. A screw configuration consisting of conveying and kneading elements was found to be effective in dispersion of the talc particles (5--10 microns) in the polyester matrix. While the rates of crystallization increased for the talc filled polyester blends, overall crystallinity reduced. Mechanical, tear and puncture properties of films made using the talc filled polyester blends were comparable to linear low density Polyethylene (LDPE). Ecoflex-Thermoplastic Starch (TPS) graft co-polymers were continuously manufactured in melt with maleic acid catalyst using a twin-screw co-rotating extruder. The graft co-polymer was completely extractable in Dichloromethane and formed transparent films on solvent casting. Regular corn-starch was maleated in a twin-screw extruder using maleic anhydride or maleic acid, glycerol plasticizer and optional radical initiator. Confirmation of reactivity of maleic acid onto the starch backbone was confirmed by Fourier Transformed Infra Red (FTIR) Spectroscopy. (Abstract shortened by UMI.)

Balakrishnan, Sunder

327

Protein specific polymeric immunomicrospheres  

NASA Technical Reports Server (NTRS)

Small, round, bio-compatible microspheres capable of covalently bonding proteins and having a uniform diameter below about 3500 A are prepared by substantially instantaneously initiating polymerization of an aqueous emulsion containing no more than 35% total monomer including an acrylic monomer substituted with a covalently bondable group such as hydroxyl, amino or carboxyl and a minor amount of a cross-linking agent.

Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

1980-01-01

328

Flame retardant polymeric materials  

SciTech Connect

The flame retardation of polyolefins is the focus of this volume. Methods for reduction of smoke and experimental evaluation of flammability parameters for polymeric materials are discussed. The flammability evaluation methods for textiles and the use of mass spectrometry for analysis of polymers and their degradation products are also presented.

Lewin, M.; Atlas, S.M.; Pearce, E.M.

1982-01-01

329

Preparation and characterization of poly(isobutyl methacrylate) microbeads with grafted amidoxime groups  

NASA Astrophysics Data System (ADS)

Poly(isobutyl methacrylate) (PiBMA) microspheres with a 800- to 1500-?m diameter range synthesized by suspension polymerization technique were used as the trunk polymer in the preparation of a highly efficient new adsorbent. Glycidyl methacrylate (GMA) was grafted onto the trunk polymer by pre-irradiation grafting technique. Grafting conditions were optimized, and GMA grafted PiBMA beads were modified with iminodiacetonitrile (IDAN) in ethanol at 80 °C. The nitrile groups were then amidoximated by using 6% (m/v) hydroxylamine hydrochloride in methanol solution. The IDAN modification and the conversion of the nitrile groups to amidoxime were followed by FT-IR spectroscopy. The surface morphology and thermal behavior of the PiBMA and its modificated forms were also characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques further confirming modification and amidoximation.

Çaykara, Tuncer; Alaslan, ?erife ?irin; Gürü, Metin; Bodugöz, Hatice; Güven, Olgun

2007-10-01

330

Autologous fat grafting in secondary breast reconstruction.  

PubMed

Autologous fat grafting has become a common technique for revisional breast surgery. The purpose of this series is to review our experience with fat grafting for the correction of acquired breast deformities. A retrospective review was performed on 107 patients with a history of breast cancer between 1996 and 2010, who had autologous fat grafting at the time of secondary breast reconstruction. The indications were for improvement in contour, shape, and volume of the breast following transverse rectus abdominis myocutaneous (TRAM) flap reconstruction (n = 55), latissimus dorsi with or without implant (n = 20), implant reconstruction (n = 20), and breast conservation therapy deformity (n = 12). The average volume of injection was 40 mL (range, 5-150 mL), the most common location being upper and medial quadrants. Fat was harvested mainly from the abdomen, thighs, and flanks. Complications occurred in 11% of the patients, and included fat necrosis, erythema, keloid scarring, and pain. Complications were higher when performed with implant reconstructions. Repeat fat injection was performed in 25% (n = 27/107), which increased with the length of follow-up. Patients with a history of radiation therapy had an increased incidence of repeat injections (36% vs. 18%). Patients with >6 months follow-up reported an improvement of about 83%. Autologous fat grafting is a safe and effective tool for secondary breast reconstruction. It is helpful in all types of reconstructions to improve contour, volume, and overall breast shape and symmetry. Repeat injections are often required and this is more common in patients with longer follow-up and in those with a history of radiation therapy. The popularity of this approach in reconstructive breast surgery will likely continue to increase. PMID:21451387

Losken, Albert; Pinell, Ximena A; Sikoro, Katherine; Yezhelyev, Maksym V; Anderson, Erica; Carlson, Grant W

2011-05-01

331

Current status of arterial grafts for coronary artery bypass grafting  

PubMed Central

For over a decade there has been accumulating evidence that the use of more than a single arterial graft during coronary artery bypass grafting can improve clinical outcomes. However the vast majority of patients in most developed countries still only receive a single arterial conduit even in the presence of multivessel coronary artery disease. This review summarizes the current evidence for the use of a second internal mammary artery and/or radial artery graft. While in comparison to vein grafts the superior patency of internal mammary artery grafts is well established, there now exists strong and consistent evidence of the superior patency of radial arteries over the longer term. Likewise, there is a rapidly growing body of evidence that the superior patency of both these arteries in comparison to vein grafts translates into improved clinical outcomes. PMID:23977618

2013-01-01

332

Periorbital fat grafting.  

PubMed

Periorbital aging is a multifactorial process involving volume loss (bone and soft tissue), tissue decent, and cutaneous degenerative changes. Traditional approaches to surgery on this area of the face have been subtractive in nature, focusing on excision of skin, muscle, and fat. This has frequently led to a gaunt or hollowed postoperative appearance. Contemporary aesthetic eyelid and periorbital rejuvenation has undergone a paradigm shift from an excisionally based surgical approach to one that prioritizes volume preservation and/or augmentation. The development of fat grafting to the eyelids and periorbita has given the eyelid surgeon a viable surgical alternative to prevent postoperative volume depletion, maintain the smooth transition of the lower eyelid to the cheek, and aid in restoring the youthful appearance desired after surgery. This article will focus of periorbital fat grafting and touch upon fat preservation techniques as primary restorative procedures or as surgical adjuncts. PMID:23426752

Massry, Guy G; Azizzadeh, Babak

2013-02-01

333

Siloxane-grafted membranes  

DOEpatents

Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional group. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

Friesen, D.T.; Obligin, A.S.

1989-10-31

334

Dacron graft aneurysm treated by endovascular stent-graft  

Microsoft Academic Search

A 72-year old man who underwent aorto-bifemoral bypass with insertion of a Dacron graft 18 years previously presented with\\u000a an aneurysm in the left limb of his graft. Angiography also demonstrated a bilateral occlusion of the popliteal arteries.\\u000a Computed tomography (CT) angiography was performed and showed a localized dilation of 3 cm in the left limb of the graft,\\u000a which

Amos Ofer; Samy Nitecki; Aaron Hoffman; Ahuva Engel

2001-01-01

335

Surface Grafted Polysarcosine as a Peptoid Antifouling Polymer Brush  

PubMed Central

Poly(N-substituted glycine) “peptoids” are a class of peptidomimetic molecules receiving significant interest as engineered biomolecules. Sarcosine (i.e. poly(N-methyl glycine)) has the simplest sidechain chemical structure of this family. In this contribution, we demonstrate that surface-grafted polysarcosine (PSAR) brushes exhibit excellent resistance to non-specific protein adsorption and cell attachment. Polysarcosine was coupled to a mussel adhesive protein inspired DOPA-Lys pentapeptide, which enabled solution grafting and control of the surface chain density of the PSAR brushes. Protein adsorption was found to decrease monotonically with increasing grafted chain densities, and protein adsorption could be completely inhibited above certain critical chain densities specific to different polysarcosine chain-lengths. The dependence of protein adsorption on chain length and density was also investigated by a molecular theory. PSAR brushes at high chain length and density were shown to resist fibroblast cell attachment over a 7 wk period, as well as resist the attachment of some clinically relevant bacteria strains. The excellent antifouling performance of PSAR may be related to the highly hydrophilic character of polysarcosine, which was evident from high-pressure liquid chromatography measurements of polysarcosine and water contact angle measurements of the PSAR brushes. Peptoids have been shown to resist proteolytic degradation and polysarcosine could be produced in large quantities by N-carboxy anhydride polymerization. In summary, surface grafted polysarcosine peptoid brushes hold great promise for antifouling applications. PMID:23101930

Lau, King Hang Aaron; Ren, Chunlai; Sileika, Tadas S.; Park, Sung Hyun; Szleifer, Igal; Messersmith, Phillip B.

2012-01-01

336

Covalent grafting of polyaniline onto aniline-terminated porous silicon  

NASA Astrophysics Data System (ADS)

This paper deals with the preparation of polyaniline (PANi) covalently grafted onto aniline-terminated porous silicon (PSi) substrate. Aniline-terminated PSi surface was obtained in a two-steps procedure. First, oxidized PSi surface was reacted with 3-bromopropyltrichlorosilane to yield a brominated surface. Aniline-terminated PSi surface was realized by reacting brominated PSi layer with aniline molecules at 60 °C for 24 h. The aniline moieties anchored onto the PSi surface were used as reactive sites for graft polymerization of aniline monomer. The composition and morphology of the resulting surfaces were examined by Fourier transform infrared spectroscopy (FT-IR), secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM). Furthermore, the optical properties of all functionalized materials involved in the synthesis protocol were characterized using photoluminescence (PL).

Chiboub, Nawel; Boukherroub, Rabah; Gabouze, Noureddine; Moulay, Saad; Naar, Nacéra; Lamouri, Saad; Sam, Sabrina

2010-05-01

337

Influence of the polymeric interphase design on the interfacial properties of (fiber-reinforced) composites.  

PubMed

In fiber-reinforced composites, the interphase nanostructure (i.e., the extended region between two phases in contact) has a pronounced influence on their interfacial adhesion. This work aims at establishing a link between the interphase design of PS-based polymeric fiber coatings and their influence on the micromechanical performance of epoxy-based composite materials. Thiol-ene photochemistry was utilized to introduce a polymeric gradient on silica-like surfaces following a two-step approach without additional photoinitiator. Two complementary grafting-techniques were adapted to modify glass fibers: "Grafting-onto" deposition of PB-b-PS diblock copolymers for thin-film coatings (thickness<20 nm) at low grafting density (<0.1 chains/nm2)--and "grafting-from" polymerization for brush-like PS homopolymer coatings of higher thickness (up to 225 nm) and higher density. Polymer-coated glass fibers were characterized for polymer content using thermogravimetric analysis (TGA) and their nanostructural morphologies by scanning electron microscopy (SEM). Model substrates of flat glass and silicon were studied by atomic force microscopy (AFM) and spectroscopic ellipsometry (SE). The change in interfacial shear strength (IFSS) due to fiber modification was determined by a single fiber pull-out experiment. Thick coatings (>40 nm) resulted in a 50% decrease in IFSS. Higher shear strength occurred for thinner coatings of homopolymer and for lower grafting densities of copolymer. Increased IFSS (10%) was found upon dilution of the surface chain density by mixing copolymers. We show that the interfacial shear strength can be increased by tailoring of the interphase design, even for systems with inherently poor adhesion. Perspectives of polymeric fiber coatings for tailored matrix-fiber compatibility and interfacial adhesion are discussed. PMID:23446425

Kuttner, Christian; Hanisch, Andreas; Schmalz, Holger; Eder, Michaela; Schlaad, Helmut; Burgert, Ingo; Fery, Andreas

2013-04-10

338

Polymeric blends for sensor and actuation dual functionality  

NASA Technical Reports Server (NTRS)

The invention described herein supplies a new class of electroactive polymeric blend materials which offer both sensing and actuation dual functionality. The blend comprises two components, one component having a sensing capability and the other component having an actuating capability. These components should be co-processable and coexisting in a phase separated blend system. Specifically, the materials are blends of a sensing component selected from the group consisting of ferroelectric, piezoelectric, pyroelectric and photoelectric polymers and an actuating component that responds to an electric field in terms of dimensional change. Said actuating component includes, but is not limited to, electrostrictive graft elastomers, dielectric electroactive elastomers, liquid crystal electroactive elastomers and field responsive polymeric gels. The sensor functionality and actuation functionality are designed by tailoring the relative fraction of the two components. The temperature dependence of the piezoelectric response and the mechanical toughness of the dual functional blends are also tailored by the composition adjustment.

St. Clair, Terry L. (Inventor); Harrison, Joycelyn S. (Inventor); Su, Ji (Inventor); Ounaies, Zoubeida (Inventor)

2004-01-01

339

Lightweight polymeric exhaust components  

US Patent & Trademark Office Database

Disclosed is a muffler assembly including: a) polymeric housing having an interior surface and at least one opening for at least one inlet and one outlet exhaust pipe; b) at least one metal inlet exhaust pipe and at least one metal outlet exhaust pipe positioned within the openings to provide housing-exhaust pipe interfaces; c) a thermal insulating material coating the interior surface of the polymeric housing and extending through the housing-exhaust pipe interfaces; wherein the thermal insulating material seals the muffler assembly at the housing-exhaust pipe interfaces; and wherein the muffler assembly has a leak rate of 105 Liters/minute or less at 4.5 psig pressure. An optional muffler assembly has body mounting adapters attached to the inlet and outlet exhaust pipes and positioned within the openings to provide housing-body mounting adapter interfaces. Also disclosed are processes for manufacturing the muffler assemblies.

2013-08-13

340

Surface polymerization agents  

SciTech Connect

This is the final report of a 1-year, Laboratory-Directed R&D project at LANL. A joint technical demonstration was proposed between US Army Missile Command (Redstone Arsenal) and LANL. Objective was to demonstrate that an unmanned vehicle or missile could be used as a platform to deliver a surface polymerization agent in such a manner as to obstruct the filters of an air-breathing mechanism, resulting in operational failure.

Taylor, C.; Wilkerson, C.

1996-12-01

341

Polymeric battery separators  

Microsoft Academic Search

Configurations of cross-linked or vulcanized amphophilic or quaternized block copolymer of haloalkyl epoxides and hydroxyl terminated alkadiene polymers are useful as battery separators in both primary and secondary batteries, particularly nickel-zinc batteries. The quaternized block copolymers are prepared by polymerizing a haloalkyl epoxide in the presence of a hydroxyl terminated 1,3-alkadiene to form a block copolymer that is then reacted

R. J. Minchak; W. N. Schenk

1985-01-01

342

Synthesis and applications of poly(2-hydroxyethylmethacrylate) grafted agar: a microwave based approach.  

PubMed

Synthesis of graft copolymers under the influence of microwave radiation alone is a rapid, efficient, clean, cheap, convenient, energy-saving and green method. Grafting of poly(2-hydroxyethylmethacrylate) on agar backbone was carried out under the influence of microwave radiation. The synthesis is optimized in terms of percentage grafting and intrinsic viscosity, by varying the microwave irradiation time and monomer (2-hydroxyethylmethacrylate) concentration. The synthesized graft copolymers have been characterized by intrinsic viscosity measurement, FTIR spectroscopy, UV-spectroscopy, elemental analysis (C, H, N, & S), thermal studies and scanning electron microscopy (SEM). Flocculation efficacy of the synthesized graft copolymers was studied in 0.25% kaolin and 1% coal fine suspension, through 'jar test' procedure. Further, flocculation efficacy of the best grade, coagulant (alum) and agar were studied for possible application in remediation of metals from river water. PMID:23850679

Rani, G Usha; Mishra, Sumit; Pathak, Gopal; Jha, Usha; Sen, Gautam

2013-10-01

343

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

2005-01-01

344

Radiation  

Cancer.gov

DCEG researchers carry out a broad-based research program designed to identify, understand, and quantify the risk of cancer in populations exposed to medical, occupational, or environmental radiation. They study ionizing radiation exposures (e.g., x-rays,

345

Oriented immobilization of proteins on grafted porous polymers  

NASA Astrophysics Data System (ADS)

The modification of polymers by radiation grafting has been utilized for several decades. The penetrability of gamma rays allows to modify the internal surfaces of porous materials retaining its mechanical properties. In recent years applications of these materials to obtain chromatographic supports and biocatalysts have been reported. In this work, we described the grafting of glycidyl methacrylate (GMA) onto a macroporous polysulfone polymer. Reproducible amount of grafting, from 10% to 60% was obtained by choosing favourable monomer concentration and gamma radiation doses from 6 kGy up. Afterwards, iminodiacetic acid (IDA) and amino phenyl arsine oxide (PAO) were covalently attached to the grafted polyGMA, in correspondence with the grafting degree. Later on, a recombinant histidin-patch thioredoxin protein (HP-rTrx) was immobilized onto this surface by two different ways, involving specific protein orientations. The first one involves an IDA-Ni 2+ complex and three HP-rTrx's histidines and the other one involves a co-ordination site between PAO and two proximal HP-rTrx's cysteines, which corresponds to the active site of the enzyme. Specific polyclonal antibodies recognize HP-rTrx on the polymer. Proper orientation of the protein was confirmed by HP-rTrx activity measurements. The described procedure allows the successful oriented immobilization of a protein onto a macroporous polysulfone material.

Carbajal, M. Laura; Smolko, Eduardo E.; Grasselli, Mariano

2003-08-01

346

[Autologous fat grafting].  

PubMed

Autologous fat grafting is a standard method for soft tissue augmentation. The method is commonly used for volume restoration of the ageing face. Furthermore, atrophic scars, lipodystrophy and scleroderma en coup de sabre can be treated. Following liposuction, the harvested fat can be reinjected immediately or stored at minus 28 degrees C for at least 2 years. In most cases, several injections at 3 to 4 months intervals are needed for good long-term effects. The procedure is used world-wide with good results and a minimum of side effects. PMID:14634748

Schmeller, W; Meier-Vollrath, I

2003-12-01

347

Synthesis of polymer\\/Laponite nanocomposite latex particles via emulsion polymerization using silylated and cation-exchanged Laponite clay platelets  

Microsoft Academic Search

We report the synthesis and characterization of polymer\\/Laponite nanocomposite latex particles through emulsion polymerization using organically modified Laponite clay platelets as seeds. Two approaches were adopted for the organic modification of Laponite. The first one is based on the grafting of either ?-methacryloyloxy propyl dimethyl-methoxysilane (?-MPDES) or ?-methacryloyloxy propyl triethoxysilane (?-MPTES) on the clay edges. The other strategy consists in

Norma Negrete-Herrera; Jean-Luc Putaux; Elodie Bourgeat-Lami

2006-01-01

348

A new approach to graft bioactive polymer on titanium implants: Improvement of MG 63 cell differentiation onto this coating.  

PubMed

Integration of titanium implants into bone is only passive and the resulting fixation is mainly mechanical in nature, with anchorage failure. Our objective, to increase the biointegration of the implant and the bone tissue, could be obtained by grafting a bioactive ionic polymer to the surface of the titanium by a covalent bond. In this paper, we report the grafting of an ionic polymer model poly(sodium styrene sulfonate) (polyNaSS), in a two-step reaction procedure. Treatment of the titanium surface by a mixture of sulfuric acid and hydrogen peroxide allows the formation of titanium hydroxide and titanium peroxide. In the second reaction step, heating of a metal implant, placed in a concentrated solution of sodium styrene sulfonate monomer (NaSS), induces the decomposition of titanium peroxides with the formation of radicals capable of initiating the polymerization of NaSS. Various parameters, such as temperature of polymerization and time of polymerization, were studied in order to optimize the yield of polyNaSS grafting. Colorimetry, Fourier-transformed infrared spectra recorded in an attenuated total reflection, X-ray photoelectron spectroscopy techniques and contact angle measurements were applied to characterize the surfaces. MG63 osteoblastic cell response was studied on polished, oxidized and grafted titanium samples. Cell adhesion, alkaline phosphatase activity and calcium nodules formation were significantly enhanced on grafted titanium samples compared to unmodified surfaces. PMID:18809363

Hélary, Gérard; Noirclère, Flavie; Mayingi, Josselin; Migonney, Véronique

2009-01-01

349

Structured polymer grafts on diamond.  

SciTech Connect

In this work, a facile method for the preparation of structured and functional polymer grafts on diamond surfaces is described. Uniform poly(styrene) (PS) grafts with a thickness of {approx}110 nm were created directly onto oxidized ultrananocrystalline diamond (UNCD) surfaces by the self-initiated photografting and photopolymerization of bulk styrene with UV irradiation. The stable covalent bonding of the PS grafts allows polymer analogue reactions with drastic reaction conditions without noticeable detachment of the polymer coating. Thus, various functionalities, such as nitro, sulfonic, and aminomethyl groups have been successfully incorporated to the polymer grafts. Furthermore, the reactivity contrast between hydrogenated and oxidized UNCD surfaces allows for the preparation of structured polymer grafts. Finally, we have demonstrated the good reactivity and accessibility of the incorporated pendant functional groups.

Steenackers, M.; Lud, S. Q.; Niedermeier, M.; Bruno, P.; Gruen, D. M.; Feulner, P.; Stutzmann, M.; Garrido, J. A.; Jordan, R.; Materials Science Division; Technische Univ. Munchen

2007-11-01

350

Synthesis of perm-selective membranes by grafting acrylic acid into air-irradiated Teflon-FEP films  

NASA Astrophysics Data System (ADS)

Grafting acrylic acid into air-irradiated Teflon-FEP films was investigated. Pre-irradiation doses ranged from 0.5 to 10 kGy. Grafting occurred at 45 or 60°C. Homopolymerization inhibitors, ferrous ions or methylene blue, were added to the system. It was found that after completion of the reaction, within 40-100 min, membranes were obtained with very low electric resistivities. The influence of added inhibitors, pre-irradiation dose and grafting temperature was studied. From the results it is concluded that the initiating centers in air-irradiated Teflon-FEP are, on the one hand, peroxides of structure POOP', in which P is a polymeric radical and Pprime; a small fragment, and on the other trapped PO .2 radicals. The latter only react after losing their oxygen. In the presence of polymerization inhibitors, initiation involves a redox process which reduces the overall activation energy.

Bozzi, Annick; Chapiro, Adolphe

351

A cation-exchange material for protein separations based on grafting of thiol-terminated sulfopropyl methacrylate telomers onto hydrophilized monodisperse divinylbenzene particles.  

PubMed

A strong cation-exchange separation material has been prepared from monodisperse divinylbenzene particles modified by a "grafting to" approach, utilizing as anchoring points epoxy groups introduced onto the surface of the particles via oxidation of residual vinyl groups. The grafted chains consisted of thiol-terminated telomers of sulfopropyl methacrylate prepared by iniferter mediated polymerization, and grafting was performed by reaction of the corresponding thiolate anion with the surface epoxy groups. Attachment through epoxy moieties that were subsequently converted into 2,3-propanediol groups increased the hydrophilicity of the polymeric particles and incubation experiments showed no signs of the proteins denaturing on the column during an extended contact time of 1 h at room temperature. The performance of the grafted material was demonstrated by the chromatographic separation of cytochrome C, lysozyme, myoglobin, and ribonuclease A, in a cation-exchange mode. PMID:18615833

Nordborg, Anna; Limé, Fredrik; Shchukarev, Andrei; Irgum, Knut

2008-07-01

352

Ethylene polymerization catalyst  

SciTech Connect

A process is described for the polymerization or co-polymerization of ethylene comprising passing ethylene with or without an alpha-olefin comonomer into contact with a vanadium catalyst under polymerization conditions, the catalyst comprising: (i) the reaction product of a vanadium trihalide wherein the halogen is chlorine, bromine, or iodine, or mixtures thereof, and an electron donor, which is a liquid organic Lewis base in which the vanadium trihalide is soluble; (ii) a modifier, BX/sub 3/ or a compound having the formula AIR/sub (3-a)/X/sub a/ wherein each R is an alkyl radical having 1 to 14 carbon atoms and is alike or different; X is chlorine, bromine, or iodine, or mixtures thereof; and a is 0, 1, or 2; (iii) a silican support into which components (i) and (ii) are impregnated; (iv) a salt admixed with the silica support, the cation of the salt being selected from Groups I and II of the Periodic Chart of the Atoms and the anion of the salt being a carbonate or a sulfate; (v) a halocarbon promoter; and (vi) a hydrocarbyl aluminum cocatalyst, wherein the molar ratio of (a) electron donor to vanadium trihalide is about 1:1 to about 20:1; (b) modifier to electron donor is about 0.1:1 to about 10:1; (c) cocatalyst to component (i) is about 5:1 to 500:1; and (d) promoter to cocatalyst is about 0.1:1 to about 10:1.

Zoeckler, M.T.; Karol, F.J.

1989-03-07

353

Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

2006-01-01

354

Polymer grafted hydroxyapatite whisker as a filler for dental composite resin with enhanced physical and mechanical properties.  

PubMed

The objective of this study was to investigate the effect of surface graft polymerization of hydroxyapatite whisker (HW) on physical and mechanical properties of dental composite resin. Poly bisphenol A glycidyl methacrylate (Poly(Bis-GMA)) was grafted onto silanized hydroxyapatite whisker (SHW) via solution polymerization and the amount of the Poly(Bis-GMA) on the surface was effectively controlled by polymerization time. The obtained poly(Bis-GMA) grafted hydroxyapatite whisker (PGHW) with different polymer contents was filled into a resin matrix respectively, meanwhile the composites with HW and with SHW served as controls. Monomer conversion was characterized by Fourier transform infrared spectroscopy (FTIR) and volume shrinkage of the composite resin was measured with a density tester. Mechanical properties were tested with a universal testing machine. The results indicated that the composite filled with PGHW-1h (graft ratio of poly(Bis-GMA): 8.5 wt.%) showed lower shrinkage and better mechanical properties, improving flexural strength by 6.5% and 11.9% compared with SHW filled composite and HW filled composite, respectively. However, PGHW with higher graft ratios aggregated seriously and formed defects in the composite, leading to deterioration of mechanical properties. It was revealed that the poly(Bis-GMA) on the surface of PGHW acted as a functional transition layer and enhanced interfacial compatibility and interaction between whisker and resin matrix, which facilitated the dispersion of PGHW in the composite and decreased the composite shrinkage. Thus, the graft polymerization of Bis-GMA on the surface of filler might be a promising modification method for the fabrication of dental materials. PMID:24094216

Liu, Fengwei; Wang, Ruili; Cheng, Yanhua; Jiang, Xiaoze; Zhang, Qinghong; Zhu, Meifang

2013-12-01

355

Perivascular Nitric Oxide Delivery to Saphenous Vein Grafts Prevents Graft Stenosis after Coronary Artery Bypass Grafting: A Novel Sheep Model  

Microsoft Academic Search

Objectives: Graft stenosis is a major complication of coronary artery bypass grafting with autologous saphenous vein grafts. Nitric oxide (NO) is believed to prevent this phenomenon. We studied the effect of perivascular application of an NO donor on the degree of stenosis of such grafts in an ovine model. Methods: Twenty white Iranian ewes were randomized to coronary artery bypass

Kyomars Abbasi; Keivan Shalileh; Maryam Sotudeh Anvari; Shahram Rabbani; Abolfazl Mahdanian; Seyed Hosein Ahmadi; Naghmeh Moshtaghi; Namvar Movahedi; Abbasali Karimi

2011-01-01

356

Amphiphilic graft copolymers from end-functionalized starches: synthesis, characterization, thin film preparation, and small molecule loading.  

PubMed

End-functionalized macromolecular starch reagents, prepared by reductive amination, were grafted onto a urethane-linked polyester-based backbone using copper-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry to produce novel amphiphilic hybrid graft copolymers. These copolymers represent the first examples of materials where the pendant chains derived from starch biopolymers have been incorporated into a host polymer by a grafting-to approach. The graft copolymers were prepared in good yields (63-90%) with high grafting efficiencies (66-98%). Rigorous quantitative spectroscopic analyses of both the macromolecular building blocks and the final graft copolymers provide a comprehensive analytical toolbox for deciphering the reaction chemistry. Due to the modular nature of both the urethane-linked polyester synthesis and the postpolymerization modification, the starch content of these novel hybrid graft copolymers was easily tuned from 28-53% (w/w). The uptake of two low molecular weight guest molecules into the hybrid polymer thin films was also studied. It was found that binding of 1-naphthol and pterostilbene correlated linearly with amount of starch present in the hybrid polymer. The newly synthesized graft copolymers were highly processable and thermally stable, therefore, opening up significant opportunities in film and coating applications. These results represent a proof-of-concept system for not only the construction of starch-containing copolymers, but also the loading of these novel polymeric materials with active agents. PMID:25033423

Ryno, Lisa M; Reese, Cassandra; Tolan, McKenzie; O'Brien, Jeffrey; Short, Gabriel; Sorriano, Gerardo; Nettleton, Jason; Fulton, Kayleen; Iovine, Peter M

2014-08-11

357

Robot-Assisted Antegrade In-Situ Fenestrated Stent Grafting  

SciTech Connect

To determine the technical feasibility of a novel approach of in-situ fenestration of aortic stent grafts by using a remotely controlled robotic steerable catheter system in the porcine model. A 65-kg pig underwent robot-assisted bilateral antegrade in-situ renal fenestration of an abdominal aortic stent graft with subsequent successful deployment of a bare metal stent into the right renal artery. A 16-mm iliac extension covered stent served as the porcine aortic endograft. Under fluoroscopic guidance, the graft was punctured with a 20-G customized diathermy needle that was introduced and kept in place by the robotic arm. The needle was exchanged for a 4 x 20 mm cutting balloon before successful deployment of the renal stent. Robot-assisted antegrade in-situ fenestration is technically feasible in a large mammalian model. The robotic system enables precise manipulation, stable positioning, and minimum instrumentation of the aorta and its branches while minimizing radiation exposure.

Riga, Celia V., E-mail: c.riga@imperial.ac.uk; Bicknell, Colin D. [Imperial College Healthcare, St Mary's Hospital, Regional Vascular Unit (United Kingdom); Wallace, Daniel [Hansen Medical (United States); Hamady, Mohamad; Cheshire, Nicholas [Imperial College Healthcare, St Mary's Hospital, Regional Vascular Unit (United Kingdom)

2009-05-15

358

Sorption of microorganisms by wide-porous agarose cryogels containing grafted aliphatic chains of different length  

Microsoft Academic Search

The possibility of fractionation of heterogeneous bacterial populations using wide-porous agarose cryogels containing grafted\\u000a aliphatic groups with the chain lengths of 4, 7, and 12 carbon atoms was demonstrated for the first time. The maximum sorption\\u000a of vegetative cells of gram-positive bacteria (60%) was shown for the polymeric carrier with the chain length of 4 carbon\\u000a atoms, while the hypometabolic

V. G. Evtyugin; A. B. Margulis; L. G. Damshkaln; V. I. Lozinsky; A. I. Kolpakov; O. N. Ilinskaya

2009-01-01

359

Surface Graft Copolymerization of Poly(vinylidene fluoride) Film with Simultaneous Lamination to Copper Foil  

Microsoft Academic Search

Surface thermal graft copolymerization with concurrent lamination was carried out between an Ar plasma pretreated poly(vinyh'dene fluoride) (PVDF) film and a copper foil in the presence of a small quantity of a N-containing monomer, such as 4-vinyl pyridine (4-VPN) and acryloyl morpholine (ACMO), under atmospheric conditions and in the complete absence of an added polymerization initiator and system degassing. The

Y. X. Liu; E. T. E. Kang; K. G. Neoh; K. L. Tan; C. C. Huan; D. J. Liaw

1999-01-01

360

Laser surface modification of polymers to improve biocompatibility: HEMA grafted PDMS, in vitro assay—III  

Microsoft Academic Search

Polydimethylsiloxane (PDMS) surface modifications were carried out using CO2-pulsed laser, without photosensitizer at ambient condition, to introduce peroxide groups onto the PDMS surface. Such peroxides were capable of initiating graft polymerization of 2-hydroxyethyl methacrylate (HEMA) onto the PDMS. The modified surfaces were characterized using a variety of techniques including scanning electron microscopy (SEM), attenuated total reflectance infrared (ATR-FTIR) and the

M. T Khorasani; H Mirzadeh; P. G Sammes

1999-01-01

361

Antioxidant–polysaccharide conjugates for food application by eco-friendly grafting procedure  

Microsoft Academic Search

In the present study, catechin–alginate and catechin–inulin conjugates were obtained by adopting free radical-induced grafting procedure. In the aim to synthesize the antioxidant–polysaccharide conjugates, ascorbic acid\\/hydrogen peroxide redox pair was employed as water-soluble and biocompatible initiator system. The insertion of catechin onto the polymeric backbones was verified by performing FT-IR, DSC and fluorescence analyses and molecular weight distributions were analyzed

U. Gianfranco Spizzirri; Ortensia Ilaria Parisi; Francesca Iemma; Giuseppe Cirillo; Francesco Puoci; Manuela Curcio; Nevio Picci

2010-01-01

362

Cationic Polymerization of Cyclic Sulfides  

Microsoft Academic Search

The mechanism of the cationic polymerization of several thietanes and of propylene sulfide under the influence of triethyloxonium tetrafluoroborate in methylene chloride is described. The thietane polymerizations stop at limited conversions because of a termination reaction occurring between the reactive chain ends (cyclic sulfonium salts) and the sulfur atoms of the polymer chain. The maximum conversions obtained under identical conditions

E. J. Goethals; W. Drijvers; D. Van Ooteghem; A. M. Buyle

1973-01-01

363

Outdoor high voltage polymeric insulators  

Microsoft Academic Search

Composite polymeric insulators are increasingly being accepted by the traditionally cautious electric utilities worldwide. They currently represent about 70% of installed new high voltage insulators in North America. The tremendous growth in the applications of non-ceramic insulators is due to their advantages over the traditional ceramic and glass insulators. However, because polymeric insulators are relatively new the expected lifetime is

R. Hackam

1998-01-01

364

Synthesis and characterization of macromolecular layers grafted to polymer surfaces  

NASA Astrophysics Data System (ADS)

The composition and behavior of surfaces and interfaces play a pivotal role in dictating the overall efficiency of the majority of polymeric materials and devices. Surface properties of the materials can be altered using surface modification techniques. It is necessary to highlight that successful methods of surface modification should affect only the upper layer of the polymer material without changing bulk properties. The processes must introduce new functionalities to the surface, optimize surface roughness, lubrication, hydrophobicity, hydrophilicity, adhesion, conductivity, and/or biocompatibility. Research presented in this dissertation is dedicated to the synthesis, characterization, and application of thin macromolecular layers anchored to polymer substrates. Specifically, attachment of functional polymers via a "grafting to" approach has been extensively studied using PET and nylon model substrates. First, poly(glycidyl methacrylate) was used to introduce permanent functionalities to the model substrates by anchoring it to model films. Then, three different functional polymers were grafted on top of the previous layer. As one part of this study, the temperature and time dependence of grafting functional layers were studied. The surface coverage by hydrophobic polymer was determined from experimental data and predicted by a model. In general, the model has a high degree of predictive capability. Next, surface modification of polymeric fibers and membranes is presented as an important application of the polymer thin layers targeted in the study. Specifically, the procedures developed for surface modification of model substrates was employed for modification of PET, nylon, and cotton fabrics as well as PET track-etched membranes. Since epoxy groups are highly reactive in various chemical reactions, the approach becomes virtually universal, allowing both various surfaces and end-functionalized macromolecules to be used in the grafted layer synthesis. PET membranes modified with a reactive anchoring layer can be successfully used to build membrane assemblies by incorporating silica, aluminum, or titanium oxide microparticles as spacers. It is expected that the proposed approaches for the surface modification of the membranes and for the generation of multilayered membrane assemblies can be employed straightforwardly to provide an efficient platform for fabrication of breathable protective materials. Characterization of modified membranes with a cantilever-based method, which can be used for prediction of properties and behavior of thin grafted films, is reported. This technique can be used as a method for fast screening of modified membranes. The method is very robust and capable of detecting very small quantities of substance adsorbed; kinetics of the process can be tracked, as well. This approach can be further developed as a handheld sensor for early warning of the presence of chemical vapors and nerve agents.

Burtovyy, Oleksandr

365

Saphenous vein graft vs. radial artery graft searching for the best second coronary artery bypass graft  

PubMed Central

Coronary artery bypass grafting (CABG) was first used in the late 1960s. This revolutionary procedure created hope among ischemic heart disease patients. Multiple conduits are used and the golden standard is the left internal mammary artery to the left anterior descending artery. Although all approaches were advocated by doctors, the use of saphenous vein grafts became the leading approach used by the majority of cardiac surgeons in the 1970s. The radial artery graft was introduced at the same time but was not as prevalent due to complications. It was reintroduced into clinical practice in 1989. The procedure was not well received initially but it has since shown superiority in patency as well as long-term survival after CABG. This review provides a summary of characteristics, technical features and patency rates of the radial artery graft in comparison with venous conduits. Current studies and research into radial artery grafts and saphenous vein grafts for CABG are explored. However, more studies are required to verify the various findings of the positive effects of coronary artery bypass grafting with the help of radial arteries on mortality and long-lasting patency. PMID:24198449

Al-Sabti, Hilal Ali; Al Kindi, Adil; Al-Rasadi, Khalid; Banerjee, Yajnavalka; Al-Hashmi, Khamis; Al-Hinai, Ali

2013-01-01

366

Organophilic Boehmite nanoparticles by ATRP methacrylates polymerization: synthesis, characterization and dispersion in polypropylene.  

PubMed

Boehmite nanoparticles covered with a polymer shell enhancing the organophilicity of the surface were prepared by physical adsorption of a polyelectrolyte atom transfer radical polymerization (ATRP) macroinitiator followed by graft-polymerization of methyl methacrylate or 2-hydroxyethyl methacrylate. The presence of polymer chains adsorbed/grafted on the Boehmite was confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy and by thermo-gravimetric analysis (TGA), which showed a significant amount of polymer covering the particles. The methodology of polymerization and the kinetics suggested the possibility to modulate the amount, type and thickness of grafted polymer shell. These organic-inorganic hybrid materials were melt compounded in a Brabender mixer with isotactic polypropylene in the presence of functionalized polypropylene. The dispersion degree of Boehmite nanoparticles in the polypropylene matrix as well as their reinforcing effect were studied by morphology characterization [scanning electron microscopy (SEM) and X-ray diffraction (XRD)], whereas thermal and thermo-mechanical properties were assessed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). PMID:18572581

Coiai, Serena; Passaglia, Elisa; Augier, Sylvain; Narducci, Piero; Ciardelli, Francesco

2008-04-01

367

Preparation of metal adsorbent from poly(methyl acrylate)-grafted-cassava starch via gamma irradiation  

NASA Astrophysics Data System (ADS)

Metal adsorbent containing hydroxamic acid groups was successfully synthesized by radiation-induced graft copolymerization of methyl acrylate (MA) onto cassava starch. The optimum conditions for grafting were studied in terms of % degree of grafting (Dg). Conversion of the ester groups present in poly(methyl acrylate)-grafted-cassava starch copolymer into hydroxamic acid was carried out by treatment with hydroxylamine (HA) in the presence of alkaline solution. The maximum percentage conversion of the ester groups of the grafted copolymer, % Dg=191 (7.63 mmol/g of MA), into the hydroxamic groups was 70% (5.35 mmol/g of MA) at the optimum condition. The adsorbent of 191%Dg had total adsorption capacities of 2.6, 1.46, 1.36, 1.15 and 1.6 mmol/g-adsorbent for Cd2+, Al3+, UO22+, V5+ and Pb2+, respectively, in the batch mode adsorption.

Suwanmala, Phiriyatorn; Hemvichian, Kasinee; Hoshina, Hiroyuki; Srinuttrakul, Wannee; Seko, Noriaki

2012-08-01

368

Grafting of HEMA onto dopamine coated stainless steel by 60Co-? irradiation method  

NASA Astrophysics Data System (ADS)

A novel method for grafting of 2-hydroxyethyl methacrylate (HEMA) onto the surface of stainless steel (SS) was explored by using 60Co-? irradiation. The surface of SS was modified by coating of dopamine before radiation grafting. The grafting reaction was performed in a simultaneous irradiation condition. The chemical structures change of the surface before and after grafting was demonstrated by Fourier transform infrared (FTIR) spectrometer. The hydrophilicity of the samples was determined by water contact angle measurement in the comparison of the stainless steel in the conditions of pristine, dopamine coated and HEMA grafted. Surface morphology of the samples was characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). The corrosion resistance properties of the samples were evaluated by Tafel polarization curve. The hemocompatibility of the samples were tested by platelet adhesion assay.

Jin, Wanqin; Yang, Liming; Yang, Wei; Chen, Bin; Chen, Jie

2014-12-01

369

Binary mixed homopolymer brushes grafted on nanorod particles: A self-consistent field theory study  

SciTech Connect

We employ the self-consistent field theory to study phase structures of brush-rod systems composed of two chemically distinct linear homopolymers. The polymer chains are uniformly grafted on the surface of a nanorod particle of finite length and comparable radius to the polymer radius of gyration. A “masking” technique treating the cylindrical boundary is introduced to solve the modified diffusion equations with an efficient and high-order accurate pseudospectral method involving fast Fourier transform on an orthorhombic cell. A rich variety of structures for the phase separated brushes is predicted. Phase diagrams involving a series of system parameters, such as the aspect ratio of the nanorod, the grafting density, and the chain length are constructed. The results indicate that the phase structure of the mixed brush-rod system can be tailored by varying the grafted chain length and/or the aspect ratio of the rod to benefit the fabrication of polymeric nanocomposites.

Ma, Xin; Yang, Yingzi; Tang, Ping, E-mail: pingtang@fudan.edu.cn, E-mail: fengqiu@fudan.edu.cn; Qiu, Feng, E-mail: pingtang@fudan.edu.cn, E-mail: fengqiu@fudan.edu.cn [Department of Macromolecular Science, The State Key Laboratory of Molecular Engineering of Polymers, Key Laboratory of Computational Physical Sciences, Fudan University, Shanghai 200433 (China)] [Department of Macromolecular Science, The State Key Laboratory of Molecular Engineering of Polymers, Key Laboratory of Computational Physical Sciences, Fudan University, Shanghai 200433 (China); Zhu, Lei [Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7202 (United States)] [Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7202 (United States); Zhao, Bin [Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996 (United States)] [Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996 (United States)

2013-12-07

370

Binary mixed homopolymer brushes grafted on nanorod particles: A self-consistent field theory study  

NASA Astrophysics Data System (ADS)

We employ the self-consistent field theory to study phase structures of brush-rod systems composed of two chemically distinct linear homopolymers. The polymer chains are uniformly grafted on the surface of a nanorod particle of finite length and comparable radius to the polymer radius of gyration. A "masking" technique treating the cylindrical boundary is introduced to solve the modified diffusion equations with an efficient and high-order accurate pseudospectral method involving fast Fourier transform on an orthorhombic cell. A rich variety of structures for the phase separated brushes is predicted. Phase diagrams involving a series of system parameters, such as the aspect ratio of the nanorod, the grafting density, and the chain length are constructed. The results indicate that the phase structure of the mixed brush-rod system can be tailored by varying the grafted chain length and/or the aspect ratio of the rod to benefit the fabrication of polymeric nanocomposites.

Ma, Xin; Yang, Yingzi; Zhu, Lei; Zhao, Bin; Tang, Ping; Qiu, Feng

2013-12-01

371

Glial grafting for demyelinating disease  

PubMed Central

Remyelination of demyelinated central nervous system (CNS) axons is considered as a potential treatment for multiple sclerosis, and it has been achieved in experimental models of demyelination by transplantation of pro-myelinating cells. However, the experiments undertaken have not addressed the need for tissue-type matching in order to achieve graft-mediated remyelination since they were performed in conditions in which the chance for graft rejection was minimized. This article focuses on the factors determining survival of allogeneic oligodendrocyte lineage cells and their contribution to the remyelination of demyelinating CNS lesions. The immune status of the CNS as well as the suitability of different models of demyelination for graft rejection studies are discussed, and ways of enhancing allogeneic oligodendrocyte-mediated remyelination are presented. Finally, the effects of glial graft rejection on host remyelination are described, highlighting the potential benefits of the acute CNS inflammatory response for myelin repair. PMID:16147541

Tepavcevic, V; Blakemore, W.F

2005-01-01

372

Radiators  

SciTech Connect

A heat-exchange radiator is connected to a fluid flow circuit by a connector which provides one member of an interengageable spigot and socket pair for push-fit, fluid-tight, engagement between the connector and the radiator, with latching formations at least one of which is resilient. Preferably the connector carries the spigot which tapers and engages with a socket of corresponding shape, the spigot carrying an O-ring seal and either latching fingers or a resilient latching circlip.

Webster, D. M.

1985-07-30

373

Switchable Adhesion from Bicomponent Polymeric Brushes  

NASA Astrophysics Data System (ADS)

We investigated the adhesive and wetting properties of bicomponent polymeric brushes made from end functionalized hydrophilic and hydrophobic polymer chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for the two polymers. Adhesive properties were tested by debonding a flat ended probe from soft pressure-sensitive-adhesives (hydrophobic & hydrophilic) and wetting properties were tested by contact angle measurements of water & diiodomethane droplets. The bicomponent brushes were chemically grafted on silicon wafers from end-functionalized chains. Wetting experiments were done directly on the wafers while for adhesion experiments, the wafers were glued on the flat end of the probe prior to the tests. In all cases the organization of the bicomponent brush could be modified reproducibly and reversibly by exposure to selective solvents. Following this strategy we succeeded to create remarkably stable adaptive polymer surfaces that can modify their adhesion and wetting reversibly and also tune them by varying the ratio of the bicomponent brush layer.

Retsos, Haris; Gorodyska, Ganna; Creton, Costantino

2005-03-01

374

Bilateral internal thoracic artery grafting  

PubMed Central

The effectiveness of the left internal mammary artery graft to the anterior descending coronary artery as a surgical strategy has been shown to improve the survival rate and decrease the risk of adverse cardiac events in patients undergoing coronary bypass surgery. These clinical benefits appear to be related to the superior short and long-term patency rates of the internal thoracic artery graft. Although the advantages of using of both internal thoracic arteries (ITA) for bypass grafting have taken longer to prove, recent results from multiple data sets now support these findings. The major advantage of bilateral ITA grafting appears to be improved survival rate, while the disadvantages of complex ITA grafting include the increased complexity of operation, and an increased risk of wound complications. While these short-term disadvantages have been mitigated in contemporary surgical practice, they have not eliminated. Bilateral ITA grafting should be considered the procedure of choice for patients undergoing coronary bypass surgery that have a predicted survival rate of longer than ten years. PMID:23977627

2013-01-01

375

Interventions in Infrainguinal Bypass Grafts  

SciTech Connect

The interventional radiologist plays an important role in the detection and prevention of infrainguinal bypass failure. Early detection and evaluation of flow-limiting lesions effectively preserve graft (venous bypass and polyester or expanded polytetrafluoroethylene bypass) patency by identifying stenoses before occlusion occurs. Delay in treatment of the at-risk graft may result in graft failure and a reduced chance of successful revascularization. For this reason, surveillance protocols form an important part of follow-up after infrainguinal bypass surgery. As well as having an understanding of the application of imaging techniques including ultrasound, MR angiography, CT angiography and digital subtraction angiography, the interventional radiologist should have detailed knowledge of the minimally invasive therapeutic options. Percutaneous transluminal angioplasty (PTA), or alternatively cutting balloon angioplasty, is the interventional treatment of choice in prevention of graft failure and occlusion. Further alternatives include metallic stent placement, fibrinolysis, and mechanical thrombectomy. Primary assisted patency rates following PTA can be up to 65% at 5 years. When the endovascular approach is unsuccessful, these therapeutic options are complemented by surgical procedures including vein patch revision, jump grafting, or placement of a new graft.

Mueller-Huelsbeck, S., E-mail: muehue@rad.uni-kiel.de; Order, B.-M.; Jahnke, T. [University Hospital Schleswig-Holstein - Campus Kiel, Department of Radiology (Germany)

2006-02-15

376

Poly(vinylidene fluoride-co-hexafluoropropylene)-graft-poly(dopamine methacrylamide) copolymers: A nonlinear dielectric material for high energy density storage  

NASA Astrophysics Data System (ADS)

A nonlinear dielectric poly(vinylidene fluoride-co-hexafluoropropylene)-graft-poly(dopamine methacrylamide) [P(VDF-HFP)-g-PDMA] graft copolymer with ultra-high energy density of 33 J/cm3 was obtained by thermally initiated radical graft polymerization. It was observed that the dielectric constant of the graft copolymer films was 63% higher than that of P(VDF-HFP), with a large dielectric breakdown strength (>850 MV/m). Theoretical analyses and experimental measurements showed that the significant improvement in the electric polarization was attributed to the introduction of the highly polarizable hydroxyl groups in the PDMA side chains, and the large breakdown strength arose from the strong adhesion bonding of the catechol-containing graft copolymer to the metal electrode.

Rahimabady, Mojtaba; Qun Xu, Li; Arabnejad, Saeid; Yao, Kui; Lu, Li; Shim, Victor P. W.; Gee Neoh, Koon; Kang, En-Tang

2013-12-01

377

Grafting titanium nitride surfaces with sodium styrene sulfonate thin films.  

PubMed

The importance of titanium nitride lies in its high hardness and its remarkable resistance to wear and corrosion, which has led to its use as a coating for the heads of hip prostheses, dental implants and dental surgery tools. However, the usefulness of titanium nitride coatings for biomedical applications could be significantly enhanced by modifying their surface with a bioactive polymer film. The main focus of the present work was to graft a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film from titanium nitride surfaces via a two-step procedure: first modifying the surface with 3-methacryloxypropyltrimethoxysilane (MPS) and then grafting the pNaSS film from the MPS modified titanium through free radical polymerization. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used after each step to characterize success and completeness of each reaction. The surface region of the titanium nitride prior to MPS functionalization and NaSS grafting contained a mixture of titanium nitride, oxy-nitride, oxide species as well as adventitious surface contaminants. After MPS functionalization, Si was detected by XPS, and characteristic MPS fragments were detected by ToF-SIMS. After NaSS grafting, Na and S were detected by XPS and characteristic NaSS fragments were detected by ToF-SIMS. The XPS determined thicknesses of the MPS and NaSS overlayers were ?1.5 and ?1.7 nm, respectively. The pNaSS film density was estimated by the toluidine blue colorimetric assay to be 260?±?70 ng/cm(2). PMID:25280842

Zorn, Gilad; Migonney, Véronique; Castner, David G

2014-09-01

378

Graft copolymers of ethyl methacrylate on waxy maize starch derivatives as novel excipients for matrix tablets: physicochemical and technological characterisation.  

PubMed

Nowadays, graft copolymers are being used as an interesting option when developing a direct compression excipient for controlled release matrix tablets. New graft copolymers of ethyl methacrylate (EMA) on waxy maize starch (MS) and hydroxypropylstarch (MHS) were synthesised by free radical polymerization and alternatively dried in a vacuum oven (OD) or freeze-dried (FD). This paper evaluates the performance of these new macromolecules and discusses the effect of the carbohydrate nature and drying process on their physicochemical and technological properties. Grafting of EMA on the carbohydrate backbone was confirmed by IR and NMR spectroscopy, and the grafting yields revealed that graft copolymers present mainly a hydrophobic character. The graft copolymerization also leads to more amorphous materials with larger particle size and lower apparent density and water content than carbohydrates (MS, MHS). All the products show a lack of flow, except MHSEMA derivatives. MSEMA copolymers underwent much plastic flow and less elastic recovery than MHSEMA copolymers. Concerning the effect of drying method, FD derivatives were characterised by higher plastic deformation and less elasticity than OD derivatives. Tablets obtained from graft copolymers showed higher crushing strength and disintegration time than tablets obtained from raw starches. This behaviour suggests that these copolymers could be used as excipients in matrix tablets obtained by direct compression and with a potential use in controlled release. PMID:19146956

Marinich, J A; Ferrero, C; Jiménez-Castellanos, M R

2009-05-01

379

Free radical polymerization-practical aspects  

SciTech Connect

This tutorial lecture will discuss practical difficulties encountered in conducting free radical initiated polymerization and how these difficulties are accomodated by bulk, solution, dispersion, suspension and emulsion polymerization techniques. Practical applications of polymeric products obtained by these polymerization techniques will also be discussed.

Harwood, H.J. [Univ. of Akron, OH (United States)

1993-12-31

380

Craniofacial Bone Grafting: Wolff's Law Revisited  

PubMed Central

Bone grafts are used for the reconstruction of congenital and acquired deformities of the facial skeleton and, as such, comprise a vital component of the craniofacial surgeon's armamentarium. A thorough understanding of bone graft physiology and the factors that affect graft behavior is therefore essential in developing a more intelligent use of bone grafts in clinical practice. This article presents a review of the basic physiology of bone grafting along with a survey of pertinent concepts and current research. The factors responsible for bone graft survival are emphasized. PMID:22110789

Oppenheimer, Adam J.; Tong, Lawrence; Buchman, Steven R.

2008-01-01

381

Polymerization of anionic wormlike micelles.  

PubMed

Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

2006-01-31

382

Polymeric optical MEMS  

NASA Astrophysics Data System (ADS)

As micro-opto-electro-mechanical systems and devices evolve from prototypes to products, the need for cost-effective mass production techniques becomes crucial. This challenging cost goal can be reached using mass replication techniques like injection molding and hot embossing.In order to meet the special demands of miniaturization these replication techniques have been modified incorporating variothermal process control, an evacuation of the mold chamber and a modification of the molding parameters including elevated temperatures. Based on these techniques numerous micro- optical systems have been developed including a twelve fold multi-fiber connectors with an average insertion loss of 0.35 dB, an optical bench using polymeric alignment structures on a silicon substrate, a 4 by 4 star coupler with passive fiber alignment, a 1 by 2 singlemode fiber switch, and a singlemode 4 by 4 optical matrix switch. In these systems geometrical tolerances of one micrometers and below have been obtained allowing passive alignment of multimode and singlemode fibers during the assembly process and high precision positioning of fibers during operation.

Hossfeld, Jens; Paatzsch, Thomas; Schulze, Jens; Neumeier, Michel; Weber, Lutz; Bauer, Hans-Dieter; Ehrfeld, Wolfgang

1999-03-01

383

Direct polymerization of proteins.  

PubMed

We report the synthesis of active polymers of superfolder green fluorescent protein (sfGFP) in one step using Click chemistry. Up to six copies of the non-natural amino acids (nnAAs) p-azido-l-phenylalanine (pAzF) or p-propargyloxy-l-phenylalanine (pPaF) were site-specifically inserted into sfGFP by cell-free protein synthesis (CFPS). sfGFP containing two or three copies of these nnAAs were coupled by copper-catalyzed azide-alkyne cycloaddition to synthesize linear or branched protein polymers, respectively. The protein polymers retained ?63% of their specific activity (i.e., fluorescence) after coupling. Polymerization of a concentrated solution of triply substituted sfGFP resulted in fluorescent macromolecular particles. Our method can be generalized to synthesize polymers of a protein or copolymers of any two or more proteins, and the conjugation sites can be determined exactly by standard genetic manipulation. Polymers of proteins and small molecules can also be created with this technology to make a new class of scaffolds or biomaterials. PMID:24200191

Albayrak, Cem; Swartz, James R

2014-06-20

384

Radioimmunoassay of circulating schistosome antigen with a radiation-immobilized monoclonal antibody : Preliminary results  

NASA Astrophysics Data System (ADS)

A two-site immunoradiometric assay with a mouse monoclonal antibody to a circulating schistosome antigen was comparatively investigated using the monoclonal antibody either absorbed to microtiter plates (reference IRMA) or immobilized by several techniques. Radiation polymerization methods were carried out at Takasaki Radiation Chemistry Research Establishment, Takasaki, Gunma (I. Kaetsu, M. Kumakura), using 2-hydroxyethyl methacrylate monomers and 1 Mrad irradiation. A significant correlation was obtained with the reference IRMA and the assay using radiation polymerization-immobilized antibody ( r = 0.94), although non-specific binding to the polymer discs was higher (x 10) than with microtiter plates. Immobilization of the monoclonal antibody onto polypropylene/polyethylene copolymer films grafted with methacrylic acid irradiated at 0.68 Mrads and treated with carbodiimide/N-hydroxysuccinimide, was carried out at the Dept of Bioengineering, University of Washington, Seattle, Washington (A.S. Hoffman, W.R. Gombotz, S. Uenoyama). A significant correlation ( r = 0.90) was obtained with the reference IRMA. Non-specific binding was also higher than with microtiter plates (x 6). An important result was the increased shelf life of the immobilized reagent.

Dessaint, J. P.; Nogueira-Queiroz, J. A.; Capron, A.

385

Seawater degradation of polymeric composites  

E-print Network

to moist environments. As this distribution of strengths shifts, a transition in failure mechanism occurs. Hypothetically, the composite would initially fail in the resin. After limited exposure to moisture one might see a localized interfacial failure... the absorption in polymer resins and subsequently in polymeric composites. Experimentation performed has made an effort to support the use of the Fickian model of absorption in polymeric composites [2, 6, 7]. Secondly, researchers studied the effect...

Grant, Timothy Sean

2012-06-07

386

Photoredox catalysis for polymerization reactions.  

PubMed

Photoredox catalysis is now well-known in organic synthesis for the formation of free radicals under very soft irradiations conditions (e.g. sunlight, household fluorescence or LED bulbs, Xe lamp). This method has been introduced here to the polymer chemistry area to initiate ring opening polymerizations (ROP) or free radical polymerizations (FRP). The present paper will give an up-to date situation of the photocatalyst achievements in FRP and ROP. PMID:22871290

Lalevée, Jacques; Tehfe, Mohamad-Ali; Morlet-Savary, Fabrice; Graff, Bernadette; Dumur, Frédéric; Gigmes, Didier; Blanchard, Nicolas; Fouassier, Jean-Pierre

2012-01-01

387

Polycaps: Reversibly formed polymeric capsules  

PubMed Central

Described are assemblies consisting of polymeric capsules, “polycaps,” formed from two calix[4]arene tetraureas covalently connected at their lower rims. In these structures self-assembly leads to reversibly formed capsule sites along a chain, reminiscent of beads on a string. Their dynamic behavior is characterized by 1H NMR spectroscopy through encapsulation of guest species, reversible polymerization, and the formation of sharply defined hybrid capsules. PMID:11038556

Castellano, Ronald K.; Rudkevich, Dmitry M.; Rebek, Julius

1997-01-01

388

Enhancing antibiofouling performance of Polysulfone (PSf) membrane by photo-grafting of capsaicin derivative and acrylic acid  

NASA Astrophysics Data System (ADS)

Biofouling is a critical issue in membrane water and wastewater treatment. Herein, antibiofouling PSf membrane was prepared by UV-assisted graft polymerization of acrylic acid (AA) and a capsaicin derivative, N-(5-methyl-3-tert-butyl-2-hydroxy benzyl) acrylamide (MBHBA), on PSf membrane. AA and MBHBA were used as hydrophilic monomer and antibacterial monomer separately. The membranes were characterized by FTIR-ATR, contact angle, SEM, AFM, cross-flow filtration unit, antifouling and antibacterial measurements. Verification of MBHBA and AA that photo-chemically grafted onto the PSf membrane surface is confirmed by carbonyl stretching vibration at ?1655 cm-1 and ?1730 cm-1, separately. The increasing AA concentration accelerates the graft-polymerization of MBHBA and resulted in a more hydrophilic surface. Consequently, antifouling property of the membranes was improved on a large level. The flux recovery rate can achieve 100% during the cyclic test, which may be attributed to the more hydrophilic and smooth surface, as well as the decreased membrane pore size. Most importantly, the presence of AA in graft co-polymer does not affect the antibacterial activity of MBHBA. That may be induced by the increasing chain length and flexibility of the grafted polymer chains.

Wang, Jian; Sun, Haijing; Gao, Xueli; Gao, Congjie

2014-10-01

389

Integration of RAFT polymerization and click chemistry to fabricate PAMPS modified macroporous polypropylene membrane for protein fouling mitigation.  

PubMed

A copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) grafting-to method was used to tether alkyne-terminated poly(2-acrylamido-2-methyl propane sulfonic acid) (alkyne-PAMPS) to the azide functionalized macroporous polypropylene membrane (MPPM-N3). Alkyne-PAMPS was synthesized by the reversible addition-fragmentation chain transfer polymerization (RAFT) of AMPS with an alkyne-terminated trithiocarbonate served as a chain transfer agent. The combination of RAFT polymerization with click chemistry to graft polymer to the surface of polypropylene membrane produced relatively high grafting density and controllable grafting chain length. The structure and composition of the modified and unmodified MPPM surfaces were analyzed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS); field emission scanning electron microscopy (FE-SEM) was employed to observe the morphological changes on the membrane surface. The permeation performances were tested by the filtration of protein dispersion. The experimental results show that with the grafting degree going up, the relative flux reduction decreases, while the relative flux recovery ratio increases, and the protein fouling is obviously mitigated by tethering PAMPS to the membrane surface. The modified membranes can be potentially applied for fouling reduction during the filtration of proteins. PMID:25217729

Wang, Yun; Wang, Li-Li; He, Xiao-Chun; Zhang, Zi-Jun; Yu, Hai-Yin; Gu, Jia-Shan

2014-12-01

390

Preparation and characterization of poly (ethylene glycol) grafted Ca-alginate fibers by ?-irradiation for biomedical applications  

Microsoft Academic Search

Radiation processing, being a physical process, is an environmentally friendly alternative to chemical modifications. It is economically viable, safe, and possesses several advantages over other conventional methods employed for modification and grafting. To improve the physico-mechanical properties of Ca-alginate fiber (CaAF), poly (ethylene glycol) (PEG) was grafted by applying ?-radiation of different intensities. The effect of ?-irradiation on the physico-mechanical,

Mohammed Mizanur Rahman; Bodrun Nesa; Romana Nasrin; Swajal Molla; Taslim Ur Rashid; Papia Haque; Ahmad I. Mustafa; Mubarak A. Khan

2012-01-01

391

Polymeric waveguide components for THz quantum cascade laser outcoupling  

NASA Astrophysics Data System (ADS)

We study the use of polymeric components to achieve efficient outcoupling of radiation from double-metal-waveguide THz quantum cascade lasers. We employ cyclicolefincopolymer to realize optical fibers with diameters between 60mm and 1000mm, and characterize their absorption coefficient at 2.9THz. We show that assembling a fiber on the facet of a singleplasmon quantum cascade laser improves its far field radiation pattern, making it narrower. We also provide a design of a broadband directional coupler that can be used to couple radiation from a doublemetal quantum cascade laser waveguide into the tapered end of a metal coated optical fiber.

Castellano, F.; Beere, H.; Ritchie, D.; Vitiello, M. S.

2014-03-01

392

Synthesis and characterization of HCl doped polyaniline grafted multi-walled carbon nanotubes core-shell nano-composite  

Microsoft Academic Search

Multi-walled carbon nanotubes (MWNTs) was modified with p-phenylenediamine (p-PDA) and hydrochloric acid (HCl) doped polyaniline (PANI) grafted MWNTs nano-composite was synthesized by in situ oxidation\\u000a polymerization. Raman spectra, XPS, TEM and XRD reveal that modification does not decrease the integrity of outer graphite\\u000a sheets in p-PDA modified MWNTs (p-MWNTs) excessively and results in phenylamine groups with concentration of 3.7% covalently grafted

Jun Xu; Pei Yao; Yanxia Wang; Fei He; Yao Wu

2009-01-01

393

Preparation and characterization of soluble and DBSA doped polyaniline grafted multi-walled carbon nanotubes nano-composite  

Microsoft Academic Search

Soluble and highly doped polyaniline (PANI) grafted multi-walled carbon nanotubes (MWNTs) nano-composite was synthesized by\\u000a in situ oxidation polymerization, de-doping with ammonium hydroxide and doping the PANI-Emeraldine base (PANI-EB) grafted\\u000a MWNTs nano-composite in N-methyl-2-pyrrolidinone (NMP) with Dodecyl benzene sulfonic acid (DBSA). Transmission electron microscope (TEM), Raman spectra,\\u000a Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and standard four-probe methods were

Pei Yao; Jun Xu; Yi Wang; Chen Zhu

2009-01-01

394

Design and fabrication of artificial skin: chitosan and gelatin immobilization on silicone by poly acrylic acid graft using a plasma surface modification method  

Microsoft Academic Search

Acrylic acid (AAc) was grafted onto the surfaces of polydimethylsiloxane (PDMS) films using a two-step oxygen plasma treatment. The first step of this method included: oxygen plasma pretreatment of the PDMS films, immersion in AAc and drying. The second step was carried out by plasma polymerization of the preadsorbed reactive AAc on the surfaces of the dried pretreated films. Then

Amir Salati; Hamid Keshvari; Soheila Kordestani; Shahrouz Taranejoo

2011-01-01

395

Plasma aminofunctionalisation of PVDF microfiltration membranes: comparison of the in plasma modifications with a grafting method using ESCA and an amino-selective fluorescent probe  

Microsoft Academic Search

Microfiltration membranes of polyvinylidenefluoride (PVDF) are promising materials for the development of functional polymeric membranes. The aim of this work is the investigation of typical plasma processes such as continuous plasma, pulse plasma and plasma graft polymerisation concerning their effect of functionalisation with primary amino groups using a mixture of nitrogen and hydrogen, ammonia, allylamine and diaminocyclohexane. The relative amounts

M Müller; C Oehr

1999-01-01

396

Synthesis of amphipathic block copolymers based on polyisobutylene and polyoxyethylene and their application in emulsion polymerization  

SciTech Connect

Polymer colloids stabilized by polymeric surfactants are of great interest both commercially and academically. It has been found that these materials enhance latex stabilization in a number of applications. The polymeric surfactants are amphipathic block and graft copolymers containing both hydrophilic and hydrophobic moieties. The current study involved the synthesis of a series of amphipathic triblock copolymers, polyisobutylene-block-polyoxyethylene-block-polyisobutylene (PIB-b-POE-b-PIB), for use in the emulsion polymerization of styrene (STY), methyl methacrylate (MMA), and vinyl acetate (VAc). The stabilizing effectiveness of these triblock copolymers was studied as a function of their blocklength. When the molecular weight of the POE center block was changed from M{sub n} = 2,000 to 20,000 g/mole, stable lattices were obtained in emulsion polymerization with MMA, STY, and VAc as the monomers. In all cases, the polymerization rates remained constant, while the number of particles/volume decreased with increasing POE chain length. When the molecular weight of the PIB end blocks was changed from M{sub n} = 400 to 2,600 g/mole keeping the molecular weight of the POE center block constant at M{sub n} = 20,000 g/mole, the poly(methyl methacrylate) and poly(vinyl acetate) lattices exhibited similar behavior, i.e., the number of particles and particle sizes remained the same, but the rate of polymerization reached a maximum at 87 wt% POE content. In the case of poly(styrene) both the rate of polymerization and the number of particles remained constant. The emulsion polymerization of other monomers such as butadiene, acrylonitrile, methyl acrylate, ethyl acrylate, and butyl acrylate was carried out by using one triblock copolymer, i.e., PIB(400)-b-POE (8,000)-b-PIB-(400). Stable lattices were also formed in all cases.

Sar, B.

1992-12-31

397

Grafting of gallic acid onto chitosan enhances antioxidant activities and alters rheological properties of the copolymer.  

PubMed

A new, simple, and effective method to graft gallic acid (GA) onto chitosan (CS) in aqueous solution in the presence of carbodiimide and hydroxybenzotriazole was developed. The grafting amount of GA reached as much as 209.9 mg/g of copolymer, which appears as the highest one among the reported literature, and the grafting degree of GA to CS was adjustable with modulation of the mass ratio of GA to CS. The covalent insertion of GA onto the polymeric backbones was confirmed by UV-vis and (1)H NMR analyses. Grafting endowed the resulting copolymer GA-grafted-CS (GA-g-CS) with both the advantages of CS and GA. The antioxidant capacity of GA-g-CS was much higher than that of the plain CS examined by assays of DPPH, superoxide, and ABTS radicals scavenging activities, reducing power, chelating power, inhibition of lipid peroxidation, ferric reducing antioxidant potential, and ?-carotene-linoleic acid assays. Particularly, GA-g-CS showed significantly higher antioxidant activity than GA in ?-carotene-linoleic acid assay. Furthermore, the viscosity of GA-g-CS was significantly higher than that of CS. The present study developed a novel approach to synthesize GA-g-CS that could be a potential biomaterial in food industries. PMID:25198516

Xie, Minhao; Hu, Bing; Wang, Yan; Zeng, Xiaoxiong

2014-09-17

398

POST CORONARY ARTERY BYPASS GRAFT STUDY (CABG)  

EPA Science Inventory

Relative effectiveness of moderate versus more aggressive lipid lowering, and of low dose anticoagulation versus placebo, in delaying saphenous vein coronary bypass graft atherosclerosis and preventing occlusion of saphenous grafts of patients with saphenous vein coronary bypass ...

399

The consequences of a failed femoropopliteal bypass grafting: Comparison of saphenous vein and PTFE grafts  

Microsoft Academic Search

Objectives: Although there are numerous reports comparing saphenous vein (SV) and polytetrafluoroethylene (PTFE) with respect to the patency rates for femoropopliteal bypass grafts, the clinical consequences of failed grafts are not as well described. This study compares the outcomes of failed SV and PTFE grafts with a specific emphasis on the degree of acute limb ischemia caused by graft occlusion.

Mark R. Jackson; Todd P. Belott; Timothy Dickason; William J. Kaiser; J. Gregory Modrall; R. James Valentine; G. Patrick Clagett

2000-01-01

400

Coating with paclitaxel improves graft survival in a porcine model of haemodialysis graft stenosis  

Microsoft Academic Search

Background. Most commonly resulting from intimal hyperplasia at the venous anastomosis, stenosis leading to thrombosis is a major cause of failure of polytetra- fluoroethylene (PTFE) dialysis grafts. We recently reported that coating haemodialysis grafts with pacli- taxel could reduce neointimal hyperplasia. This study tested whether paclitaxel-coating could prolong graft survival in a porcine model. Methods. PTFE grafts were double-coated with

Byung Ha Lee; Jung Eun Lee; Kwang Woong Lee; Hye Yeong Nam; Hyun Jung Jeon; Young Ju Sung; Jong Sung Kim; Hyun Jung Lim; Jong-sang Park; Jai Young Ko; Dae Joong Kim

2007-01-01

401

Surface active properties of polyoxyethylene macromonomers and their role in radical polymerization in disperse systems.  

PubMed

Conventional dispersion polymerization and copolymerization of low-molecular weight (conventional) unsaturated monomers allows preparation of monodisperse and micronsize polymer particles. A similar behavior can be found in the surfactant-free dispersion polymerization of non-traditional vinyl monomers, unsaturated macromonomers. The latter systems allow preparation of random, comb-like, star-like and graft copolymers as well. An interesting alternative arises with the use of amphiphilic reactive macromonomers that contain a polymerizable group and aggregate into an organized structure -- a micelle. Under such conditions the high rate of polymerization and ultrafine (microparticles) polymer dispersions are generated. Thus, the surface-active macromonomers promote the formation of micelles and polymer growth within the main reaction loci -- polymer particles. Furthermore, the surface-active compounds can be formed during the copolymerization of hydrophilic macromonomer and hydrophobic low-molecular weight comonomer. The reactive surface-active oligomeric radicals are incorporated into the polymer matrix or the particle surface layer, which prevents them from subsequent migration. Besides, the covalently bound surface-active groups at the particle surface strongly increase the colloidal stability of final polymer dispersion. This article presents a review of the current literature in the field of the surfactant-free dispersion polymerization of the polyoxyethylene unsaturated macromonomers. Besides a short introduction into some kinetic aspects of radical polymerization of traditional monomers in homogeneous and disperse systems, we mainly focus on the organized aggregation of amphiphilic polyoxyethylene macromonomers, the characterization of amphiphilic graft copolymers and their aggregation properties, and radical copolymerization of polyoxyethylene macromonomers. We discuss the birth and growth of chains, the transfer of reaction loci from the continuous phase to polymer particles, the diffusion-controlled termination, association of amphiphilic reaction by-products, the particle growth by agglomeration, the particle nucleation, the deactivation of polymer chain growth and the colloidal stability. Effects of initiator type and concentration, the surface activity of macromonomer, the macromonomer type and concentration, temperature, additives and the type of continuous phase on the kinetics of polymerization, and colloidal parameters of the reaction system are also evaluated. Variation of the polymer coil density, the polymer-polymer interaction, and polymer-solvent interaction with the molecular weight, diluent and method (light scattering, the size exclusion, etc.) are discussed. Polymerization of macromonomers provides regularly branched polymers with varied branching density. Since both the degree of polymerization and the length of branches may be varied, polymeric materials with specific properties can be prepared. PMID:11130017

Capek, I

2000-12-26

402

Synthesis of Externally Initiated Poly(3-alkylthiophene)s via Kumada Catalyst Transfer Polymerization  

NASA Astrophysics Data System (ADS)

The ability of chemists to design and synthesize pi conjugated organic polymers with precise control over their physical and electronic properties remains the key to technological breakthroughs using polymeric material in electronic and photonic devices. Kumada catalyst transfer polymerization (KCTP) technique and Grignard metathesis (GRIM) method have enabled the synthesis of highly regioregular polymers with controlled molecular weights, narrow polydispersity index and uniform end groups. Applying this technique toward external initiation of polymers would enable the preparation of sophisticated and beneficial polymer architectures such as surface grafted polymers. This work presents an investigation of various mechanistic parameters for external initiation of poly(3-alkylthiophene). The effects of binding ligand variation on the Nickel catalyst were investigated utilizing a novel methodology allowing facile screening of ligands. Poly(3-hexylthiophene) was synthesized with high percentage initiator headgroup incorporation with triphenylphosphine ligand while the use of bidentate ligands such as diphenylphosphinopropane only resulted in quantitative initiation when ligand exchange followed initiation with the more active species. A variety of functionally substituted aryl and thiophene halides were explored for their potential to act as external small molecule initiators and the reaction intermediates were characterized via spectroscopic techniques as well as theoretical calculations. Aryl halides were found to be more stable than thiophene halides and the type and position of the initiator functionality has played a deciding role in the polymerization mechanism. Ortho substitution stabilized the aryl-Ni intermediate complex via favorable orbital overlap and kinetic effects as a result of steric hindrance were demonstrated to affect the success of the external initiation. Surface-grafted poly(3-methylthiophene) thin films were synthesized from indium tin oxide where polymer thin film thicknesses were regulated by the variation of monomer solution and polymerization time. Photoelectron spectroscopy analysis had demonstrated that electrochemical oxidation of surface grafted thin films affords the ability to tune the work function and ionization potential. Such materials with controllable thicknesses and electronic properties have the potential to be useful as components in organic photovoltaic devices.

D'Avanzo, Antonella

403

VUV modification promotes endothelial cell proliferation on PTFE vascular grafts  

NASA Astrophysics Data System (ADS)

Small diameter (?6 mm ID ) synthetic vascular grafts, used as lower-limb vessel replacements in patients without suitable autologous saphenous veins, have a failure rate of 53% after 4 yr. Graft failure is due to thrombosis and intimal hyperplasia, an increase in smooth muscle cells in the lumen of the vessel which leads to progressive closing and ultimate occlusion of the vessel. In an effort to increase patency rates of synthetic grafts, investigators have seeded vascular grafts with endothelial cells prior to implantation in an attempt to control both thrombosis and smooth muscle proliferation. This technique has been successful for the development of an endothelial monolayer in animal trials, but has met with limited success in humans. The hydrophobicity, low surface energy, and weak electrical charge of expanded polytetrafluoroethylene (ePTFE) provides conditions which are not optimal for endothelial cell attachment. The purpose of this study is to evaluate the effect of vacuum ultraviolet (VUV) modification of ePTFE on endothelial cell adhesion and proliferation. Pieces of ePTFE graft material were exposed to 10, 20 or 40 W VUV radiation for 10, 20 or 40 min using a UV excimer lamp. Prior to cell adhesion and proliferation experiments, the grafts pieces were autoclaved and cut into pledgets. Half of the pledgets were precoated with fibronectin ( 20 ?g/ml). Cell adhesion was measured by seeding 3H-thymidine labeled human umbilical vein endothelial cells (HUVEC) onto the pledgets for 60 min. The pledgets were then washed and the remaining radioactivity assayed using scintillation counting. For the cell proliferation experiments, pledgets were seeded with unlabeled HUVEC which were allowed to adhere to the graft material for 18 h. The cells were then exposed to 3H-thymidine ( 1 ?Ci/ml) for approximately 48 h and then washed to remove any unincorporated 3H-thymidine. Incorporation of 3H-thymidine was measured using scintillation counting. Four replicate samples each, with and without fibronectin, were evaluated for each power and exposure time for both the adhesion and proliferation experiments. VUV modification had no effect on cell adhesion for all power levels studied. In addition, it appears that cell adhesion is independent of the presence of fibronectin. Cell proliferation, on the other hand, is augmented by modification, especially in the presence of fibronectin. These results suggest that VUV modification may provide a better surface for endothelial cell colonization of synthetic vascular grafts.

Cezeaux, J. L.; Romoser, C. E.; Benson, R. S.; Buck, C. K.; Sackman, J. E.

1998-05-01

404

[Radioindication of bone graft healing].  

PubMed

To control the state of transplanted bone in different terms following the plastic procedure a radioisotope study by strontium-85 was performed in 29 patients. The results of scannography (in 31 cases) and radiometry (in 42 cases) were analysed. The determination of the character of strontium-85 distribution and the intensity of its accumulation in the operated extremity makes it possible to assess the graft condition and the intensity of osteogenesis a greater precision and earlier than does roentgenography. Radioisotope investigation conducted dynamically enable the prognostication of the course of the graft healing process. PMID:333749

Kuznetsova, L B; Pavlova, L P; Kondrat'ev, V G; Khmelev, O N

1977-01-01

405

Left ventricular assist device outflow graft: alternative sites  

PubMed Central

We describe three alternative approaches for the left ventricular assist device (LVAD) outflow graft during implantation of the LVAD. The supraceliac abdominal aorta, innominate artery and left axillary artery were employed as alternative sites for the LVAD outflow graft in the setting of a heavily calcified ascending aorta or a hostile chest wall and mediastinum. The first approach involved the use of the supraceliac abdominal aorta. Given that the patient had a history of multiple previous breast surgeries and chest wall radiation for breast cancer treatment, a left subcostal incision was employed as a sternotomy-sparing approach. The second approach was the use of the innominate artery in a patient with a porcelain ascending aorta. The patient underwent pulmonary valve replacement, right ventricle outflow tract reconstruction and tricuspid valve annuloplasty in addition to the LVAD implantation. The third approach was the use of the left axillary artery. This patient had a history of LVAD implantation and subsequently developed infection with pseudoaneurysm formation at the aortic anastomosis of the outflow graft. We conclude that the supraceliac abdominal aorta, the innominate artery and the left axillary artery are potential alternative routes for the LVAD outflow graft in the settings of heavily calcified ascending aorta or a hostile chest wall and mediastinum. Although the described alternative approaches are safe and viable options, we highly recommend utilizing these approaches only in selected patients with significantly higher risks and hazards to the standard surgical approach.

Aftab, Muhammad; Singh, Steve K.; Mallidi, Hari R.; Frazier, Oscar H.

2014-01-01

406

Polymer brush covalently attached to OH-functionalized mica surface via surface-initiated ATRP: control of grafting density and polymer chain length.  

PubMed

The controlled grafting density of poly(tert-butyl acrylate) was studied on OH-activated mica substrates via surface-initiated atom-transfer radical polymerization (ATRP). By properly adjusting parameters such as the immobilization reaction time and the concentration of an ATRP initiator, a wide range of initiator surface coverages and hence polymer densities on mica were possible. The covalently immobilized initiator successfully promoted the polymerization of tert-butyl acrylate on mica surfaces. The resulting polymer layer thickness was measured by AFM using a step-height method. Linear relationships of the polymer thickness with respect to the molecular weight of the free polymer and with respect to the monomer conversion were observed, suggesting that ATRP is well controlled and relatively densely end-grafted layers were obtained. The polymer grafting density controlled by adjusting the initiator surface coverage was confirmed by the polymer layer swelling capacity and film thickness measurements. PMID:19256467

Lego, Béatrice; François, Marion; Skene, W G; Giasson, Suzanne

2009-05-01

407

Cyst arising in a free bone graft  

Microsoft Academic Search

A cyst which arose in an autogenous iliac crest bone graft is presented. The cyst developed unilaterally 8 years following secondary alveolar bone grafting. The cyst, which was lined by a pseudostratified ciliated columnar epithelium, is believed to be the result of implantation of small particles of nasal epithelium into the bone transplant during the grafting procedure.

C. Lekkas; L. M. H. Smets; F. van Hoeken

2001-01-01

408

Preparation of polymer-clay nanocomposites via dispersion polymerization using tailor-made polymeric surface modifiers.  

E-print Network

??ENGLISH ABSTRACT: Fully exfoliated polystyrene-clay nanocomposites were prepared via free radical polymerization in dispersion polymerization, in a mixture of ethanol and water. Sodium montomorillonite clay… (more)

Nagi, Greesh

2011-01-01

409

Stereospecific olefin polymerization catalysts  

DOEpatents

A metallocene catalyst system is described for the polymerization of {alpha}-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula shown wherein: R{sup 1}, R{sup 2}, and R{sup 3} are independently selected from the group consisting of hydrogen, C{sub 1} to C{sub 10} alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C{sub 1} to C{sub 10} alkyls as a substituent, C{sub 6} to C{sub 15} aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R{sup 8}){sub 3} where R{sup 8} is selected from the group consisting of C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; R{sup 4} and R{sup 6} are substituents both having van der Waals radii larger than the van der Waals radii of groups R{sup 1} and R{sup 3}; R{sup 5} is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E{sup 1}, E{sup 2} are independently selected from the group consisting of Si(R{sup 9}){sub 2}, Si(R{sup 9}){sub 2}--Si(R{sup 9}){sub 2}, Ge(R{sup 9}){sub 2}, Sn(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}--C(R{sup 9}){sub 2}, where R{sup 9} is C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; and the ligand may have C{sub S} or C{sub 1}-symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from {alpha}-olefin monomers.

Bercaw, J.E.; Herzog, T.A.

1998-01-13

410

High-energy radiation and polymers: A review of commercial processes and emerging applications  

NASA Astrophysics Data System (ADS)

Ionizing radiation has been found to be widely applicable in modifying the structure and properties of polymers, and can be used to tailor the performance of either bulk materials or surfaces. Fifty years of research in polymer radiation chemistry has led to numerous applications of commercial and economic importance, and work remains active in the application of radiation to practical uses involving polymeric materials. This paper provides a survey of radiation-processing methods of industrial interest, ranging from technologies already commercially well established, through innovations in the active R&D stage which show exceptional promise for future commercial use. Radiation-processing technologies are discussed under the following categories: cross-linking of plastics and rubbers, curing of coatings and inks, heat-shrink products, fiber-matrix composites, chain-scission for processing control, surface modification, grafting, hydrogels, sterilization, natural product enhancement, plastics recycling, ceramic precursors, electronic property materials, ion-track membranes and lithography for microdevice production. In addition to new technological innovations utilizing conventional gamma and e-beam sources, a number of promising new applications make use of novel radiation types which include ion beams (heavy ions, light ions, highly focused microscopic beams and high-intensity pulses), soft X-rays which are focused, coherent X-rays (from a synchrotron) and e-beams which undergo scattering to generate patterns.

Clough, R. L.

2001-12-01

411

Self-Assembled Polymeric Micelles Based on Hyaluronic Acid-g-Poly(d,l-lactide-co-glycolide) Copolymer for Tumor Targeting  

PubMed Central

Graft copolymer composed hyaluronic acid (HA) and poly(d,l-lactide-co-glycolide) (PLGA) (HAgLG) was synthesized for antitumor targeting via CD44 receptor of tumor cells. The carboxylic end of PLGA was conjugated with hexamethylenediamine (HMDA) to have amine end group in the end of chain (PLGA-amine). PLGA-amine was coupled with carboxylic acid of HA. Self-assembled polymeric micelles of HAgLG have spherical morphologies and their sizes were around 50–200 nm. Doxorubicin (DOX)-incorporated polymeric micelles were prepared by dialysis procedure. DOX was released over 4 days and its release rate was accelerated by the tumoric enzyme hyaluronidase. To assess targetability of polymeric micelles, CD44-positive HepG2 cells were employed treated with fluorescein isothiocyanate (FITC)-labeled polymeric micelles. HepG2 cells strongly expressed green fluorescence at the cell membrane and cytosol. However, internalization of polymeric micelles were significantly decreased when free HA was pretreated to block the CD44 receptor. Furthermore, the CD44-specific anticancer activity of HAgLG polymeric micelles was confirmed using CD44-negative CT26 cells and CD44-positive HepG2 cells. These results indicated that polymeric micelles of HaLG polymeric micelles have targetability against CD44 receptor of tumor cells. We suggest HAgLG polymeric micelles as a promising candidate for specific drug targeting. PMID:25216338

Son, Gyung Mo; Kim, Hyun Yul; Ryu, Je Ho; Chu, Chong Woo; Kang, Dae Hwan; Park, Su Bum; Jeong, Young-IL

2014-01-01

412

Anomalous electrical and optical properties of polymeric carbons  

NASA Astrophysics Data System (ADS)

Semiconducting polymeric carbons were prepared by pyrolyzing phenol formaldehyde resin in a nitrogen atmosphere between 500 to 800 °C for 0.5 to 48 h. Their logarithmic resistivity values were found to vary linearly with the temperature in the range of 20 to 200 °C. Properties such as switching, radiative recombination, and Mott's minimum metallic conductivity were observed in these materials. These three characteristics, which are common with the inorganic amorphous semiconductors, suggest that these polymeric carbons can be included in the class of materials which satisfy the Ioffe-Regel condition, kL?1 (where k is the electron wave vector and L is the mean-free path). The switching and the radiative recombination phenomena observed in these materials provide experimental proof for the double injection model proposed by N. F. Mott [Adv. Phys. 16, 4 (1967)] for describing conduction processes in amorphous chalcogenide semiconductors.

Chellappa, V.; Jang, B. Z.

1995-04-01

413

Polymer grafting surface as templates for the site-selective metallization  

NASA Astrophysics Data System (ADS)

We report a simple, low-cost and universal method for the fabrication of copper circuit patterns on a wide range of flexible polymeric substrates. This method relies on procedures to modify the polymeric substrates with grafted polymer template to form surface-bound N-containing groups, which can bind palladium catalysts that subsequently initiate the site-selective deposition of copper granular layer patterns. The fabrications of patterned copper films were demonstrated on three kinds of flexible polymeric films including poly(imide) (PI), poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) with minimum feature sizes of 200 ?m. The films were characterized by ATR FT-IR, contact angle, XPS, XRD, TEM, SEM. Furthermore, the copper layered structure shows good adhesion with polymeric film. This method, which provides a promising strategy for the fabrication of copper circuit patterns on flexible polymeric substrates, has the potential in manufacturing conductive features adopted in various fields including modern electronics, opto-electronics and photovoltaic applications.

Yang, Fang; Li, Peiyuan; Li, Xiangcheng; Huo, Lini; Chen, Jinhao; Chen, Rui; Na, Wei; Tang, Wanning; Liang, Lifang; Su, Wei

2013-06-01